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  • Is return-type-(only)-polymorphism in Haskell a good thing?

    - by dainichi
    One thing that I've never quite come to terms with in Haskell is how you can have polymorphic constants and functions whose return type cannot be determined by their input type, like class Foo a where foo::Int -> a Some of the reasons that I do not like this: Referential transparency: "In Haskell, given the same input, a function will always return the same output", but is that really true? read "3" return 3 when used in an Int context, but throws an error when used in a, say, (Int,Int) context. Yes, you can argue that read is also taking a type parameter, but the implicitness of the type parameter makes it lose some of its beauty in my opinion. Monomorphism restriction: One of the most annoying things about Haskell. Correct me if I'm wrong, but the whole reason for the MR is that computation that looks shared might not be because the type parameter is implicit. Type defaulting: Again one of the most annoying things about Haskell. Happens e.g. if you pass the result of functions polymorphic in their output to functions polymorphic in their input. Again, correct me if I'm wrong, but this would not be necessary without functions whose return type cannot be determined by their input type (and polymorphic constants). So my question is (running the risk of being stamped as a "discussion quesion"): Would it be possible to create a Haskell-like language where the type checker disallows these kinds of definitions? If so, what would be the benefits/disadvantages of that restriction? I can see some immediate problems: If, say, 2 only had the type Integer, 2/3 wouldn't type check anymore with the current definition of /. But in this case, I think type classes with functional dependencies could come to the rescue (yes, I know that this is an extension). Furthermore, I think it is a lot more intuitive to have functions that can take different input types, than to have functions that are restricted in their input types, but we just pass polymorphic values to them. The typing of values like [] and Nothing seems to me like a tougher nut to crack. I haven't thought of a good way to handle them. I doubt I am the first person to have had thoughts like these. Does anybody have links to good discussions about this Haskell design decision and the pros/cons of it?

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  • Do I need a helper column, or can I do this with a formula?

    - by dwwilson66
    I am using this formula =IF((LEFT($B26,2)="<p"),0,IF($B26="",0,IF($F26<>"",0,(FIND("""../",$B26))))) To parse data similar to the following. <nobr>&nbsp;&nbsp;&nbsp;&nbsp;contractor information</nobr><br> &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;<a href="../City_Electrical_Inspectors.htm"><b> City Electrical Inspectors</b></a><br> <nobr>&nbsp;&nbsp;&nbsp;&nbsp;<a href="../City_Electrical_Inspectors.htm"><b>inspection</b></a></nobr><br> My problem comes in cases such as the first line, in which the line is not a new paragraph nor a link, and my FIND returns an error of #VALUE! Id like to create an IF test to scan the line for the existence of the pattern in my FIND statement before processing that statement. I figured that looking for an error condition may be the way to go. However, the only way I can envision this is as a self-referential formula, similart to the following pseudocode. IF(ISERROR($L26)=TRUE,$L26=0,L$26=the-result-of-the-formula-above) Can this be done with a formula or do I need to use a new helper column? Thanks.

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  • How to generate DELETE statements in PL/SQL, based on the tables FK relations?

    - by The chicken in the kitchen
    Is it possible via script/tool to generate authomatically many delete statements based on the tables fk relations, using Oracle PL/SQL? In example: I have the table: CHICKEN (CHICKEN_CODE NUMBER) and there are 30 tables with fk references to its CHICKEN_CODE that I need to delete; there are also other 150 tables foreign-key-linked to that 30 tables that I need to delete first. Is there some tool/script PL/SQL that I can run in order to generate all the necessary delete statements based on the FK relations for me? (by the way, I know about cascade delete on the relations, but please pay attention: I CAN'T USE IT IN MY PRODUCTION DATABASE, because it's dangerous!) I'm using Oracle DataBase 10G R2. This is the result I've written, but it is not recursive: This is a view I have previously written, but of course it is not recursive! CREATE OR REPLACE FORCE VIEW RUN ( OWNER_1, CONSTRAINT_NAME_1, TABLE_NAME_1, TABLE_NAME, VINCOLO ) AS SELECT OWNER_1, CONSTRAINT_NAME_1, TABLE_NAME_1, TABLE_NAME, '(' || LTRIM ( EXTRACT (XMLAGG (XMLELEMENT ("x", ',' || COLUMN_NAME)), '/x/text()'), ',') || ')' VINCOLO FROM ( SELECT CON1.OWNER OWNER_1, CON1.TABLE_NAME TABLE_NAME_1, CON1.CONSTRAINT_NAME CONSTRAINT_NAME_1, CON1.DELETE_RULE, CON1.STATUS, CON.TABLE_NAME, CON.CONSTRAINT_NAME, COL.POSITION, COL.COLUMN_NAME FROM DBA_CONSTRAINTS CON, DBA_CONS_COLUMNS COL, DBA_CONSTRAINTS CON1 WHERE CON.OWNER = 'TABLE_OWNER' AND CON.TABLE_NAME = 'TABLE_OWNED' AND ( (CON.CONSTRAINT_TYPE = 'P') OR (CON.CONSTRAINT_TYPE = 'U')) AND COL.TABLE_NAME = CON1.TABLE_NAME AND COL.CONSTRAINT_NAME = CON1.CONSTRAINT_NAME --AND CON1.OWNER = CON.OWNER AND CON1.R_CONSTRAINT_NAME = CON.CONSTRAINT_NAME AND CON1.CONSTRAINT_TYPE = 'R' GROUP BY CON1.OWNER, CON1.TABLE_NAME, CON1.CONSTRAINT_NAME, CON1.DELETE_RULE, CON1.STATUS, CON.TABLE_NAME, CON.CONSTRAINT_NAME, COL.POSITION, COL.COLUMN_NAME) GROUP BY OWNER_1, CONSTRAINT_NAME_1, TABLE_NAME_1, TABLE_NAME; ... and it contains the error of using DBA_CONSTRAINTS instead of ALL_CONSTRAINTS... Please pay attention to this: http://stackoverflow.com/questions/485581/generate-delete-statement-from-foreign-key-relationships-in-sql-2008/2677145#2677145 Another user has just written it in SQL SERVER 2008, anyone is able to convert to Oracle 10G PL/SQL? I am not able to... :-( This is the code written by another user in SQL SERVER 2008: DECLARE @COLUMN_NAME AS sysname DECLARE @TABLE_NAME AS sysname DECLARE @IDValue AS int SET @COLUMN_NAME = '<Your COLUMN_NAME here>' SET @TABLE_NAME = '<Your TABLE_NAME here>' SET @IDValue = 123456789 DECLARE @sql AS varchar(max) ; WITH RELATED_COLUMNS AS ( SELECT QUOTENAME(c.TABLE_SCHEMA) + '.' + QUOTENAME(c.TABLE_NAME) AS [OBJECT_NAME] ,c.COLUMN_NAME FROM PBANKDW.INFORMATION_SCHEMA.COLUMNS AS c WITH (NOLOCK) INNER JOIN PBANKDW.INFORMATION_SCHEMA.TABLES AS t WITH (NOLOCK) ON c.TABLE_CATALOG = t.TABLE_CATALOG AND c.TABLE_SCHEMA = t.TABLE_SCHEMA AND c.TABLE_NAME = t.TABLE_NAME AND t.TABLE_TYPE = 'BASE TABLE' INNER JOIN ( SELECT rc.CONSTRAINT_CATALOG ,rc.CONSTRAINT_SCHEMA ,lkc.TABLE_NAME ,lkc.COLUMN_NAME FROM PBANKDW.INFORMATION_SCHEMA.REFERENTIAL_CONSTRAINTS rc WITH (NOLOCK) INNER JOIN PBANKDW.INFORMATION_SCHEMA.KEY_COLUMN_USAGE lkc WITH (NOLOCK) ON lkc.CONSTRAINT_CATALOG = rc.CONSTRAINT_CATALOG AND lkc.CONSTRAINT_SCHEMA = rc.CONSTRAINT_SCHEMA AND lkc.CONSTRAINT_NAME = rc.CONSTRAINT_NAME INNER JOIN PBANKDW.INFORMATION_SCHEMA.TABLE_CONSTRAINTS tc WITH (NOLOCK) ON rc.CONSTRAINT_CATALOG = tc.CONSTRAINT_CATALOG AND rc.CONSTRAINT_SCHEMA = tc.CONSTRAINT_SCHEMA AND rc.UNIQUE_CONSTRAINT_NAME = tc.CONSTRAINT_NAME INNER JOIN PBANKDW.INFORMATION_SCHEMA.KEY_COLUMN_USAGE rkc WITH (NOLOCK) ON rkc.CONSTRAINT_CATALOG = tc.CONSTRAINT_CATALOG AND rkc.CONSTRAINT_SCHEMA = tc.CONSTRAINT_SCHEMA AND rkc.CONSTRAINT_NAME = tc.CONSTRAINT_NAME WHERE rkc.COLUMN_NAME = @COLUMN_NAME AND rkc.TABLE_NAME = @TABLE_NAME ) AS j ON j.CONSTRAINT_CATALOG = c.TABLE_CATALOG AND j.CONSTRAINT_SCHEMA = c.TABLE_SCHEMA AND j.TABLE_NAME = c.TABLE_NAME AND j.COLUMN_NAME = c.COLUMN_NAME ) SELECT @sql = COALESCE(@sql, '') + 'DELETE FROM ' + [OBJECT_NAME] + ' WHERE ' + [COLUMN_NAME] + ' = ' + CONVERT(varchar, @IDValue) + CHAR(13) + CHAR(10) FROM RELATED_COLUMNS PRINT @sql Thank to Charles, this is the latest not working release of the software, I have added a parameter with the OWNER because the referential integrities propagate through about 5 other Oracle users (!!!): CREATE OR REPLACE PROCEDURE delete_cascade ( parent_table VARCHAR2, parent_table_owner VARCHAR2) IS cons_name VARCHAR2 (30); tab_name VARCHAR2 (30); tab_name_owner VARCHAR2 (30); parent_cons VARCHAR2 (30); parent_col VARCHAR2 (30); delete1 VARCHAR (500); delete2 VARCHAR (500); delete_command VARCHAR (4000); CURSOR cons_cursor IS SELECT constraint_name, r_constraint_name, table_name, constraint_type FROM all_constraints WHERE constraint_type = 'R' AND r_constraint_name IN (SELECT constraint_name FROM all_constraints WHERE constraint_type IN ('P', 'U') AND table_name = parent_table AND owner = parent_table_owner) AND delete_rule = 'NO ACTION'; CURSOR tabs_cursor IS SELECT DISTINCT table_name FROM all_cons_columns WHERE constraint_name = cons_name; CURSOR child_cols_cursor IS SELECT column_name, position FROM all_cons_columns WHERE constraint_name = cons_name AND table_name = tab_name; BEGIN FOR cons IN cons_cursor LOOP cons_name := cons.constraint_name; parent_cons := cons.r_constraint_name; SELECT DISTINCT table_name, owner INTO tab_name, tab_name_owner FROM all_cons_columns WHERE constraint_name = cons_name; delete_cascade (tab_name, tab_name_owner); delete_command := ''; delete1 := ''; delete2 := ''; FOR col IN child_cols_cursor LOOP SELECT DISTINCT column_name INTO parent_col FROM all_cons_columns WHERE constraint_name = parent_cons AND position = col.position; IF delete1 IS NULL THEN delete1 := col.column_name; ELSE delete1 := delete1 || ', ' || col.column_name; END IF; IF delete2 IS NULL THEN delete2 := parent_col; ELSE delete2 := delete2 || ', ' || parent_col; END IF; END LOOP; delete_command := 'delete from ' || tab_name_owner || '.' || tab_name || ' where (' || delete1 || ') in (select ' || delete2 || ' from ' || parent_table_owner || '.' || parent_table || ');'; INSERT INTO ris VALUES (SEQUENCE_COMANDI.NEXTVAL, delete_command); COMMIT; END LOOP; END; / In the cursor CONS_CURSOR I have added the condition: AND delete_rule = 'NO ACTION'; in order to avoid deletion in case of referential integrities with DELETE_RULE = 'CASCADE' or DELETE_RULE = 'SET NULL'. Now I have tried to turn from stored procedure to stored function, but the delete statements are not correct: CREATE OR REPLACE FUNCTION deletecascade ( parent_table VARCHAR2, parent_table_owner VARCHAR2) RETURN VARCHAR2 IS cons_name VARCHAR2 (30); tab_name VARCHAR2 (30); tab_name_owner VARCHAR2 (30); parent_cons VARCHAR2 (30); parent_col VARCHAR2 (30); delete1 VARCHAR (500); delete2 VARCHAR (500); delete_command VARCHAR (4000); AT_LEAST_ONE_ITERATION NUMBER DEFAULT 0; CURSOR cons_cursor IS SELECT constraint_name, r_constraint_name, table_name, constraint_type FROM all_constraints WHERE constraint_type = 'R' AND r_constraint_name IN (SELECT constraint_name FROM all_constraints WHERE constraint_type IN ('P', 'U') AND table_name = parent_table AND owner = parent_table_owner) AND delete_rule = 'NO ACTION'; CURSOR tabs_cursor IS SELECT DISTINCT table_name FROM all_cons_columns WHERE constraint_name = cons_name; CURSOR child_cols_cursor IS SELECT column_name, position FROM all_cons_columns WHERE constraint_name = cons_name AND table_name = tab_name; BEGIN FOR cons IN cons_cursor LOOP AT_LEAST_ONE_ITERATION := 1; cons_name := cons.constraint_name; parent_cons := cons.r_constraint_name; SELECT DISTINCT table_name, owner INTO tab_name, tab_name_owner FROM all_cons_columns WHERE constraint_name = cons_name; delete1 := ''; delete2 := ''; FOR col IN child_cols_cursor LOOP SELECT DISTINCT column_name INTO parent_col FROM all_cons_columns WHERE constraint_name = parent_cons AND position = col.position; IF delete1 IS NULL THEN delete1 := col.column_name; ELSE delete1 := delete1 || ', ' || col.column_name; END IF; IF delete2 IS NULL THEN delete2 := parent_col; ELSE delete2 := delete2 || ', ' || parent_col; END IF; END LOOP; delete_command := 'delete from ' || tab_name_owner || '.' || tab_name || ' where (' || delete1 || ') in (select ' || delete2 || ' from ' || parent_table_owner || '.' || parent_table || ');' || deletecascade (tab_name, tab_name_owner); INSERT INTO ris VALUES (SEQUENCE_COMANDI.NEXTVAL, delete_command); COMMIT; END LOOP; IF AT_LEAST_ONE_ITERATION = 1 THEN RETURN ' where COD_CHICKEN = V_CHICKEN AND COD_NATION = V_NATION;'; ELSE RETURN NULL; END IF; END; / Please assume that V_CHICKEN and V_NATION are the criteria to select the CHICKEN to delete from the root table: the condition is: "where COD_CHICKEN = V_CHICKEN AND COD_NATION = V_NATION" on the root table.

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  • Agile Database Techniques: Effective Strategies for the Agile Software Developer – book review

    - by DigiMortal
       Agile development expects mind shift and developers are not the only ones who must be agile. Every chain is as strong as it’s weakest link and same goes also for development teams. Agile Database Techniques: Effective Strategies for the Agile Software Developer by Scott W. Ambler is book that calls also data professionals to be part of agile development. Often are DBA-s in situation where they are not part of application development and later they have to survive large set of applications that all use databases different way. Of course, only some of these applications are not problematic when looking what database server has to do to serve them. I have seen many applications that rape database servers because developers have no clue what is going on in database (~3K queries to database per web application request – have you seen something like this? I have…) Agile Database Techniques covers some object and database design technologies and gives suggestions to development teams about topics they need help or assistance by DBA-s. The book is also good reading for DBA-s who usually are not very strong in object technologies. You can take this book as bridge between these two worlds. I think teams that build object applications that use databases should buy this book and try at least one or two projects out with Ambler’s suggestions. Table of contents Foreword by Jon Kern. Foreword by Douglas K. Barry. Acknowledgments. Introduction. About the Author. Part One: Setting the Foundation. Chapter 1: The Agile Data Method. Chapter 2: From Use Cases to Databases — Real-World UML. Chapter 3: Data Modeling 101. Chapter 4: Data Normalization. Chapter 5: Class Normalization. Chapter 6: Relational Database Technology, Like It or Not. Chapter 7: The Object-Relational Impedance Mismatch. Chapter 8: Legacy Databases — Everything You Need to Know But Are Afraid to Deal With. Part Two: Evolutionary Database Development. Chapter 9: Vive L’ Évolution. Chapter 10: Agile Model-Driven Development (AMDD). Chapter 11: Test-Driven Development (TDD). Chapter 12: Database Refactoring. Chapter 13: Database Encapsulation Strategies. Chapter 14: Mapping Objects to Relational Databases. Chapter 15: Performance Tuning. Chapter 16: Tools for Evolutionary Database Development. Part Three: Practical Data-Oriented Development Techniques. Chapter 17: Implementing Concurrency Control. Chapter 18: Finding Objects in Relational Databases. Chapter 19: Implementing Referential Integrity and Shared Business Logic. Chapter 20: Implementing Security Access Control. Chapter 21: Implementing Reports. Chapter 22: Realistic XML. Part Four: Adopting Agile Database Techniques. Chapter 23: How You Can Become Agile. Chapter 24: Bringing Agility into Your Organization. Appendix: Database Refactoring Catalog. References and Suggested Reading. Index.

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  • Why Cornell University Chose Oracle Data Masking

    - by Troy Kitch
    One of the eight Ivy League schools, Cornell University found itself in the unfortunate position of having to inform over 45,000 University community members that their personal information had been breached when a laptop was stolen. To ensure this wouldn’t happen again, Cornell took steps to ensure that data used for non-production purposes is de-identified with Oracle Data Masking. A recent podcast highlights why organizations like Cornell are choosing Oracle Data Masking to irreversibly de-identify production data for use in non-production environments. Organizations often copy production data, that contains sensitive information, into non-production environments so they can test applications and systems using “real world” information. Data in non-production has increasingly become a target of cyber criminals and can be lost or stolen due to weak security controls and unmonitored access. Similar to production environments, data breaches in non-production environments can cost millions of dollars to remediate and cause irreparable harm to reputation and brand. Cornell’s applications and databases help carry out the administrative and academic mission of the university. They are running Oracle PeopleSoft Campus Solutions that include highly sensitive faculty, student, alumni, and prospective student data. This data is supported and accessed by a diverse set of developers and functional staff distributed across the university. Several years ago, Cornell experienced a data breach when an employee’s laptop was stolen.  Centrally stored backup information indicated there was sensitive data on the laptop. With no way of knowing what the criminal intended, the university had to spend significant resources reviewing data, setting up service centers to handle constituent concerns, and provide free credit checks and identity theft protection services—all of which cost money and took time away from other projects. To avoid this issue in the future Cornell came up with several options; one of which was to sanitize the testing and training environments. “The project management team was brought in and they developed a project plan and implementation schedule; part of which was to evaluate competing products in the market-space and figure out which one would work best for us.  In the end we chose Oracle’s solution based on its architecture and its functionality.” – Tony Damiani, Database Administration and Business Intelligence, Cornell University The key goals of the project were to mask the elements that were identifiable as sensitive in a consistent and efficient manner, but still support all the previous activities in the non-production environments. Tony concludes,  “What we saw was a very minimal impact on performance. The masking process added an additional three hours to our refresh window, but it was well worth that time to secure the environment and remove the sensitive data. I think some other key points you can keep in mind here is that there was zero impact on the production environment. Oracle Data Masking works in non-production environments only. Additionally, the risk of exposure has been significantly reduced and the impact to business was minimal.” With Oracle Data Masking organizations like Cornell can: Make application data securely available in non-production environments Prevent application developers and testers from seeing production data Use an extensible template library and policies for data masking automation Gain the benefits of referential integrity so that applications continue to work Listen to the podcast to hear the complete interview.  Learn more about Oracle Data Masking by registering to watch this SANS Institute Webcast and view this short demo.

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  • MySQL Cluster 7.3: On-Demand Webinar and Q&A Available

    - by Mat Keep
    The on-demand webinar for the MySQL Cluster 7.3 Development Release is now available. You can learn more about the design, implementation and getting started with all of the new MySQL Cluster 7.3 features from the comfort and convenience of your own device, including: - Foreign Key constraints in MySQL Cluster - Node.js NoSQL API  - Auto-installation of higher performance distributed, clusters We received some great questions over the course of the webinar, and I wanted to share those for the benefit of a broader audience. Q. What Foreign Key actions are supported: A. The core referential actions defined in the SQL:2003 standard are implemented: CASCADE RESTRICT NO ACTION SET NULL Q. Where are Foreign Keys implemented, ie data nodes or SQL nodes? A. They are implemented in the data nodes, therefore can be enforced for both the SQL and NoSQL APIs Q. Are they compatible with the InnoDB Foreign Key implementation? A. Yes, with the following exceptions: - InnoDB doesn’t support “No Action” constraints, MySQL Cluster does - You can choose to suspend FK constraint enforcement with InnoDB using the FOREIGN_KEY_CHECKS parameter; at the moment, MySQL Cluster ignores that parameter. - You cannot set up FKs between 2 tables where one is stored using MySQL Cluster and the other InnoDB. - You cannot change primary keys through the NDB API which means that the MySQL Server actually has to simulate such operations by deleting and re-adding the row. If the PK in the parent table has a FK constraint on it then this causes non-ideal behaviour. With Restrict or No Action constraints, the change will result in an error. With Cascaded constraints, you’d want the rows in the child table to be updated with the new FK value but, the implicit delete of the row from the parent table would remove the associated rows from the child table and the subsequent implicit insert into the parent wouldn’t reinstate the child rows. For this reason, an attempt to add an ON UPDATE CASCADE where the parent column is a primary key will be rejected. Q. Does adding or dropping Foreign Keys cause downtime due to a schema change? A. Nope, this is an online operation. MySQL Cluster supports a number of on-line schema changes, ie adding and dropping indexes, adding columns, etc. Q. Where can I see an example of node.js with MySQL Cluster? A. Check out the tutorial and download the code from GitHub Q. Can I use the auto-installer to support remote deployments? How about setting up MySQL Cluster 7.2? A. Yes to both! Q. Can I get a demo Check out the tutorial. You can download the code from http://labs.mysql.com/ Go to Select Build drop-down box Q. What is be minimum internet speen required for Geo distributed cluster with synchronous replication? A. if you're splitting you cluster between sites then we recommend a network latency of 20ms or less. Alternatively, use MySQL asynchronous replication where the latency of your WAN doesn't impact the latency of your reads/writes. Q. Where you can one learn more about the PayPal project with MySQL Cluster? A. Take a look at the following - you'll find press coverage, a video and slides from their keynote presentation  So, if you want to learn more, listen to the new MySQL Cluster 7.3 on-demand webinar  MySQL Cluster 7.3 is still in the development phase, so it would be great to get your feedback on these new features, and things you want to see!

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  • SQL SERVER – Shard No More – An Innovative Look at Distributed Peer-to-peer SQL Database

    - by pinaldave
    There is no doubt that SQL databases play an important role in modern applications. In an ideal world, a single database can handle hundreds of incoming connections from multiple clients and scale to accommodate the related transactions. However the world is not ideal and databases are often a cause of major headaches when applications need to scale to accommodate more connections, transactions, or both. In order to overcome scaling issues, application developers often resort to administrative acrobatics, also known as database sharding. Sharding helps to improve application performance and throughput by splitting the database into two or more shards. Unfortunately, this practice also requires application developers to code transactional consistency into their applications. Getting transactional consistency across multiple SQL database shards can prove to be very difficult. Sharding requires developers to think about things like rollbacks, constraints, and referential integrity across tables within their applications when these types of concerns are best handled by the database. It also makes other common operations such as joins, searches, and memory management very difficult. In short, the very solution implemented to overcome throughput issues becomes a bottleneck in and of itself. What if database sharding was no longer required to scale your application? Let me explain. For the past several months I have been following and writing about NuoDB, a hot new SQL database technology out of Cambridge, MA. NuoDB is officially out of beta and they have recently released their first release candidate so I decided to dig into the database in a little more detail. Their architecture is very interesting and exciting because it completely eliminates the need to shard a database to achieve higher throughput. Each NuoDB database consists of at least three or more processes that enable a single database to run across multiple hosts. These processes include a Broker, a Transaction Engine and a Storage Manager.  Brokers are responsible for connecting client applications to Transaction Engines and maintain a global view of the network to keep track of the multiple Transaction Engines available at any time. Transaction Engines are in-memory processes that client applications connect to for processing SQL transactions. Storage Managers are responsible for persisting data to disk and serving up records to the Transaction Managers if they don’t exist in memory. The secret to NuoDB’s approach to solving the sharding problem is that it is a truly distributed, peer-to-peer, SQL database. Each of its processes can be deployed across multiple hosts. When client applications need to connect to a Transaction Engine, the Broker will automatically route the request to the most available process. Since multiple Transaction Engines and Storage Managers running across multiple host machines represent a single logical database, you never have to resort to sharding to get the throughput your application requires. NuoDB is a new pioneer in the SQL database world. They are making database scalability simple by eliminating the need for acrobatics such as sharding, and they are also making general administration of the database simpler as well.  Their distributed database appears to you as a user like a single SQL Server database.  With their RC1 release they have also provided a web based administrative console that they call NuoConsole. This tool makes it extremely easy to deploy and manage NuoDB processes across one or multiple hosts with the click of a mouse button. See for yourself by downloading NuoDB here. Reference: Pinal Dave (http://blog.SQLAuthority.com) Filed under: CodeProject, PostADay, SQL, SQL Authority, SQL Query, SQL Server, SQL Tips and Tricks, SQLServer, T SQL, Technology Tagged: NuoDB

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  • Data in two databases, eager spool resulting in query

    - by Valkyrie
    I have two databases in SQL2k5: one that holds a large amount of static data (SQL Database 1) (never updated but frequently inserted into) and one that holds relational data (SQL Database 2) related to the static data. They're separated mainly because of corporate guidelines and business requirements: assume for the following problem that combining them is not practical. There are places in SQLDB2 that PKs in SQLDB1 are referenced; triggers control the referential integrity, since cross-database relationships are troublesome in SQL Server. BUT, because of the large amount of data in SQLDB1, I'm getting eager spools on queries that join from the Id in SQLDB2 that references the data in SQLDB1. (With me so far? Maybe an example will help:) SELECT t.Id, t.Name, t2.Company FROM SQLDB1.table t INNER JOIN SQLDB2.table t2 ON t.Id = t2.FKId This query results in a eager spool that's 84% of the load of the query; the table in SQLDB1 has 35M rows, so it's completely choking this query. I can't create a view on the table in SQLDB1 and use that as my FK/index; it doesn't want me to create a constraint based on a view. Anyone have any idea how I can fix this huge bottleneck? (Short of putting the static data in the first db: believe me, I've argued that one until I'm blue in the face to no avail.) Thanks! valkyrie Edit: also can't create an indexed view because you can't put schemabinding on a view that references a table outside the database where the view resides. Dang it.

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  • Updating a Foreign Key constraint with ON DELETE CASCADE not updating?

    - by Alastair Pitts
    We've realised in our SQL Server 2005 DB that some Foreign Keys don't have the On Delete Cascade property set, which is giving us a couple of referential errors when we try and delete some records. Use the Management Studio I scripted the DROP and CREATESQL's, but it seems that the CREATE isn't working correctly. The DROP: USE [FootprintReports] GO IF EXISTS (SELECT * FROM sys.foreign_keys WHERE object_id = OBJECT_ID(N'[dbo].[FK__SUBSCRIPTIONS_Reports]') AND parent_object_id = OBJECT_ID(N'[dbo].[_SUBSCRIPTIONS]')) ALTER TABLE [dbo].[_SUBSCRIPTIONS] DROP CONSTRAINT [FK__SUBSCRIPTIONS_Reports] and the CREATE USE [FootprintReports] GO ALTER TABLE [dbo].[_SUBSCRIPTIONS] WITH CHECK ADD CONSTRAINT [FK__SUBSCRIPTIONS_Reports] FOREIGN KEY([PARAMETER_ReportID]) REFERENCES [dbo].[Reports] ([ID]) ON DELETE CASCADE GO ALTER TABLE [dbo].[_SUBSCRIPTIONS] CHECK CONSTRAINT [FK__SUBSCRIPTIONS_Reports] If I manually change the value of the On Delete in the GUI, after dropping and recreating, the On Delete isn't correctly updated. As a test, I set the Delete rule in the GUI to Set Null. It dropped correctly, and recreated without error. If I got back into the GUI, it is still showing the Set Null as the Delete Rule. Have I done something wrong? or is there another way to edit a constraint to add the ON DELETE CASCADE rule?

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  • Mapping self-table one-to-many using non-PK clolumns

    - by Harel Moshe
    Hey, i have a legacy DB to which a Person object is mapped, having a collection of family-members, like this: class Person { ... string Id; /* 9-digits string */ IList<Person> Family; ... } The PERSON table seems like: Id: CHAR(9), PK FamilyId: INT, NOT NULL and several other non-relevant columns. I'm trying to map the Family collection to the PERSON table using the FamilyId column, which is not the PK as mentioned above. So, i actually have a one-to-many which is self-table-referential. I'm getting an error saying 'Cast is not valid' when my mapping looks like this: ... <set name="Family" table="Person" lazy="false"> <key column="FamilyId" /> <one-to-many class="Person" /> </set> ... because obviously, the join NHibernate is trying to make is between the PK column, Id, and the 'secondary' column, FamilyId, instead of joining the FamilyId column to itself. Any ideas please?

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  • Copying a subset of data to an empty database with the same schema

    - by user193655
    I would like to export part of a database full of data to an empty database. Both databases has the same schema. I want to maintain referential integrity. To simplify my cases it is like this: MainTable has the following fields: 1) MainID integer PK 2) Description varchar(50) 3) ForeignKey integer FK to MainID of SecondaryTable SecondaryTable has the following fields: 4) MainID integer PK (referenced by (3)) 5) AnotherDescription varchar(50) The goal I'm trying to accomplish is "export all records from MainTable using a WHERE condition", for example all records where MainID < 100. To do it manually I shuold first export all data from SecondaryTable contained in this select: select * from SecondaryTable ST outer join PrimaryTable PT on ST.MainID=PT.MainID then export the needed records from MainTable: select * from MainTable where MainID < 100. This is manual, ok. Of course my case is much much much omre complex, I have 200+ tables, so donig it manually is painful/impossible, I have many cascading FKs. Is there a way to force the copy of main table only "enforcing referntial integrity". so that my query is something like: select * from MainTable where MainID < 100 WITH "COPYING ALL FK sources" In this cases also the field (5) will be copied. ====================================================== Is there a syntax or a tool to do this? Table per table I'd like to insert conditions (like MainID <100 is only for MainTable, but I have also other tables).

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  • one table is shared between several websites

    - by sami
    I have a static table that's shared by several websites. By static, I mean that the data is read but never updated by the websites. Currently, all websites are served from the same server but that may change. I want to minimize the need for creating/maintaining this table for each of the websites, so I thought about turning it to an xml file that's stored in a shared library that all websites have access to. The problem is I use an ORM and use forign key constraints to ensure integrity of the ids used from that table, so by removing that table out of the MySQL database into an XML file, will this affect the integrity of the ids coming from that table? My table looks like this <table name="entry"> <column name="id" type="INTEGER" primaryKey="true" autoIncrement="true" /> <column name="title" type="VARCHAR" size="500" required="true" /> </table> and I use it as a foreign key in other tables <table name="refer"> <column name="id" type="INTEGER" primaryKey="true" autoIncrement="true" /> <column name="linkto" type="INTEGER"/> <foreign-key foreignTable="entry"> <reference local="linkto" foreign="id" /> </foreign-key> </table> So I'm wondering if I remove that table out of the database, is there a way to retain that referential integrity? And of course are these any other efficient ways to do the same thing? I just don't want to have to repeat that table for several websites.

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  • Generic version control strategy for select table data within a heavily normalized database

    - by leppie
    Hi Sorry for the long winded title, but the requirement/problem is rather specific. With reference to the following sample (but very simplified) structure (in psuedo SQL), I hope to explain it a bit better. TABLE StructureName { Id GUID PK, Name varchar(50) NOT NULL } TABLE Structure { Id GUID PK, ParentId GUID (FK to Structure), NameId GUID (FK to StructureName) NOT NULL } TABLE Something { Id GUID PK, RootStructureId GUID (FK to Structure) NOT NULL } As one can see, Structure is a simple tree structure (not worried about ordering of children for the problem). StructureName is a simplification of a translation system. Finally 'Something' is simply something referencing the tree's root structure. This is just one of many tables that need to be versioned, but this one serves as a good example for most cases. There is a requirement to version to any changes to the name and/or the tree 'layout' of the Structure table. Previous versions should always be available. There seems to be a few possibilities to tackle this issue, like copying the entire structure, but most approaches causes one to 'loose' referential integrity. Example if one followed this approach, one would have to make a duplicate of the 'Something' record, given that the root structure will be a new record, and have a new ID. Other avenues of possible solutions are looking into how Wiki's handle this or go a lot further and look how proper version control systems work. Currently, I feel a bit clueless how to proceed on this in a generic way. Any ideas will be greatly appreciated. Thanks leppie

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  • how can i set up a uniqueness constraint in mysql for columns that can be null?

    - by user299689
    I know that in MySQL, UNIQUE constraits don't treat NULL values as equal. So if I have a unique constraint on ColumnX, then two separate rows can have values of NULL for ColumnX and this wouldn't violate the constraint. How can I work around this? I can't just set the value to an arbitrary constant that I can flag, because ColumnX in my case is actually a foreign key to another table. What are my options here? Please note that this table also has an "id" column that is its primary key. Since I'm using Ruby on Rails, it's important to keep this id column as the primary key. Note 2: In reality, my unique key encompasses many columns, and some of them have to be null, because they are foreign keys, and only one of them should be non-null. What I'm actually trying to do is to "simulate" a polymorphic relationship in a way that keep referential integrity in the db, but using the technique outlined in the first part of the question asked here: http://stackoverflow.com/questions/922184/why-can-you-not-have-a-foreign-key-in-a-polymorphic-association

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  • How can I make Access think there is a primary key

    - by user3692757
    I have a table and I'm trying to join it with another table, but it doesn't have a distinctive primary key. The two tables do share similarities, “Acct” and “Location”. If I could concatenate “Acct&Location” it would become a primary key, but Access won’t let me make a primary key from a calculation. I provided a small sample below. Each hospital has an “Acct”, but the “Acct” will show up once for each “Location”. How can I make join these in a relationship? I connected the two in a relationships and tried to “Enforce Referential Integrity”, but it indicated “No unique index found for the referenced field of the primary key”. Also, if I run a “Find UnMatched Query” it doesn’t find anything. I think its because I can’t make it realize that in combination “Acct” and “Location” can be perceived as primary keys when used in conjunction of each other. Acct 1 2 3 1 2 3 1 2 3| Location ABI ABI ABI NHO NHO NHO NTX NTX NTX I tried to load an image to illustrate it better, but I haven't made enough post.

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  • Why do I get this exception? {An item with the same key has already been added."})

    - by Alan
    Aknittel NewSellerID is the result of a lookup on tblSellers. These tables (tblSellerListings and tblSellers) are not "officially" joined with a foreign key relationship, either in the model or in the database, but I want some referential integrity maintained for the future. So my issue remains. Why do I get the exception ({"An item with the same key has already been added."}) with this code, if I don't begin each iteration of the foreach loop with a new ObjectContext and end it with SaveChanges, which I think will affect performance. Also, could you tell me why ORCSolutionsDataService.tblSellerListings (An ADO.NET DataServices/WCF object is not IDisposable, like LINQ to Entities?? ============================================== // Add listings to previous seller int NewSellerID = 0; // Look up existing Seller key using SellerUniqueEBAYID var qryCurrentSeller = from s in service.tblSellers where s.SellerEBAYUserID == SellerUserID select s; foreach (var s in qryCurrentSeller) NewSellerID = s.SellerID; // Save the selected listings for this seller foreach (DataGridViewRow dgr in dgvRows) { ORCSolutionsDataService.tblSellerListings NewSellerListing = new ORCSolutionsDataService.tblSellerListings(); NewSellerListing.ItemID = dgr.Cells["txtSellerItemID"].Value.ToString(); NewSellerListing.Title = dgr.Cells["txtSellerItemTitle"].Value.ToString(); NewSellerListing.CurrentPrice = Convert.ToDecimal(dgr.Cells["txtSellerItemPrice"].Value); NewSellerListing.QuantitySold = Convert.ToInt32(dgr.Cells["txtSellerItemSold"].Value); NewSellerListing.EndTime = Convert.ToDateTime(dgr.Cells["txtSellerItemEnds"].Value); NewSellerListing.CategoryName = dgr.Cells["txtSellerItemCategory"].Value.ToString(); NewSellerListing.ExtendedPrice = Convert.ToDecimal(dgr.Cells["txtExtendedReceipts"].Value); NewSellerListing.RetrievedDtime = Convert.ToDateTime(dtSellerDataRetrieved.ToString()); NewSellerListing.SellerID = NewSellerID; service.AddTotblSellerListings(NewSellerListing); } service.SaveChanges(); } catch (Exception ex) { MessageBox.Show("Unable to add a new case. Exception: " + ex.Message); }

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  • Migrate from MySQL to PostgreSQL on Linux (Kubuntu)

    - by Dave Jarvis
    Storyline Trying to migrate a database from MySQL to PostgreSQL. All the documentation I have read covers, in great detail, how to migrate the structure. I have found very little documentation on migrating the data. The schema has 13 tables (which have been migrated successfully) and 9 GB of data. MySQL version: 5.1.x PostgreSQL version: 8.4.x I want to use the R programming language to analyze the data using SQL select statements; PostgreSQL has PL/R, but MySQL has nothing (as far as I can tell). A long time ago in a galaxy far, far away... Create the database location (/var has insufficient space; also dislike having the PostgreSQL version number everywhere -- upgrading would break scripts!): sudo mkdir -p /home/postgres/main sudo cp -Rp /var/lib/postgresql/8.4/main /home/postgres sudo chown -R postgres.postgres /home/postgres sudo chmod -R 700 /home/postgres sudo usermod -d /home/postgres/ postgres All good to here. Next, restart the server and configure the database using these installation instructions: sudo apt-get install postgresql pgadmin3 sudo /etc/init.d/postgresql-8.4 stop sudo vi /etc/postgresql/8.4/main/postgresql.conf Change data_directory to /home/postgres/main sudo /etc/init.d/postgresql-8.4 start sudo -u postgres psql postgres \password postgres sudo -u postgres createdb climate pgadmin3 Use pgadmin3 to configure the database and create a schema. A New Hope The episode began in a remote shell known as bash, with both databases running, and the installation of a command with a most unusual logo: SQL Fairy. perl Makefile.PL sudo make install sudo apt-get install perl-doc (strangely, it is not called perldoc) perldoc SQL::Translator::Manual Extract a PostgreSQL-friendly DDL and all the MySQL data: sqlt -f DBI --dsn dbi:mysql:climate --db-user user --db-password password -t PostgreSQL > climate-pg-ddl.sql mysqldump --skip-add-locks --complete-insert --no-create-db --no-create-info --quick --result-file="climate-my.sql" --databases climate --skip-comments -u root -p The Database Strikes Back Recreate the structure in PostgreSQL as follows: pgadmin3 (switch to it) Click the Execute arbitrary SQL queries icon Open climate-pg-ddl.sql Search for TABLE " replace with TABLE climate." (insert the schema name climate) Search for on " replace with on climate." (insert the schema name climate) Press F5 to execute This results in: Query returned successfully with no result in 122 ms. Replies of the Jedi At this point I am stumped. Where do I go from here (what are the steps) to convert climate-my.sql to climate-pg.sql so that they can be executed against PostgreSQL? How to I make sure the indexes are copied over correctly (to maintain referential integrity; I don't have constraints at the moment to ease the transition)? How do I ensure that adding new rows in PostgreSQL will start enumerating from the index of the last row inserted (and not conflict with an existing primary key from the sequence)? Resources A fair bit of information was needed to get this far: https://help.ubuntu.com/community/PostgreSQL http://articles.sitepoint.com/article/site-mysql-postgresql-1 http://wiki.postgresql.org/wiki/Converting_from_other_Databases_to_PostgreSQL#MySQL http://pgfoundry.org/frs/shownotes.php?release_id=810 http://sqlfairy.sourceforge.net/ Thank you!

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  • DBCC CHECKDB (BatmanDb, REPAIR_ALLOW_DATA_LOSS) &ndash; Are you Feeling Lucky?

    - by David Totzke
    I’m currently working for a client on a PowerBuilder to WPF migration.  It’s one of those “I could tell you, but I’d have to kill you” kind of clients and the quick-lime pits are currently occupied by the EMC tech…but I’ve said too much already. At approximately 3 or 4 pm that day users of the Batman[1] application here in Gotham[1] started to experience problems accessing the application.  Batman[2] is a document management system here that also integrates with the ERP system.  Very little goes on here that doesn’t involve Batman in some way.  The errors being received seemed to point to network issues (TCP protocol error, connection forcibly closed by the remote host etc…) but the real issue was much more insidious. Connecting to the database via SSMS and performing selects on certain tables underlying the application areas that were having problems started to reveal the issue.  You couldn’t do a SELECT * FROM MyTable without it bombing and giving the same error noted above.  A run of DBCC CHECKDB revealed 14 tables with corruption.  One of the tables with issues was the Document table.  Pretty central to a “document management” system.  Information was obtained from IT that a single drive in the SAN went bad in the night.  A new drive was in place and was working fine.  The partition that held the Batman database is configured for RAID Level 5 so a single drive failure shouldn’t have caused any trouble and yet, the database is corrupted.  They do hourly incremental backups here so the first thing done was to try a restore.  A restore of the most recent backup failed so they worked backwards until they hit a good point.  This successful restore was for a backup at 3AM – a full day behind.  This time also roughly corresponds with the time the SAN started to report the drive failure.  The plot thickens… I got my hands on the output from DBCC CHECKDB and noticed a pattern.  What’s sad is that nobody that should have noticed the pattern in the DBCC output did notice.  There was a rush to do things to try and recover the data before anybody really understood what was wrong with it in the first place.  Cooler heads must prevail in these circumstances and some investigation should be done and a plan of action laid out or you could end up making things worse[3].  DBCC CHECKDB also told us that: repair_allow_data_loss is the minimum repair level for the errors found by DBCC CHECKDB Yikes.  That means that the database is so messed up that you’re definitely going to lose some stuff when you repair it to get it back to a consistent state.  All the more reason to do a little more investigation into the problem.  Rescuing this database is preferable to having to export all of the data possible from this database into a new one.  This is a fifteen year old application with about seven hundred tables.  There are TRIGGERS everywhere not to mention the referential integrity constraints to deal with.  Only fourteen of the tables have an issue.  We have a good backup that is missing the last 24 hours of business which means we could have a “do-over” of yesterday but that’s not a very palatable option either. All of the affected tables had TEXT columns and all of the errors were about LOB data types and orphaned off-row data which basically means TEXT, IMAGE or NTEXT columns.  If we did a SELECT on an affected table and excluded those columns, we got all of the rows.  We exported that data into a separate database.  Things are looking up.  Working on a copy of the production database we then ran DBCC CHECKDB with REPAIR_ALLOW_DATA_LOSS and that “fixed” everything up.   The allow data loss option will delete the bad rows.  This isn’t too horrible as we have all of those rows minus the text fields from out earlier export.  Now I could LEFT JOIN to the exported data to find the missing rows and INSERT them minus the TEXT column data. We had the restored data from the good 3AM backup that we could now JOIN to and, with fingers crossed, recover the missing TEXT column information.  We got lucky in that all of the affected rows were old and in the end we didn’t lose anything.  :O  All of the row counts along the way worked out and it looks like we dodged a major bullet here. We’ve heard back from EMC and it turns out the SAN firmware that they were running here is apparently buggy.  This thing is only a couple of months old.  Grrr…. They dispatched a technician that night to come and update it .  That explains why RAID didn’t save us. All-in-all this could have been a lot worse.  Given the root cause here, they basically won the lottery in not losing anything. Here are a few links to some helpful posts on the SQL Server Engine blog.  I love the title of the first one: Which part of 'REPAIR_ALLOW_DATA_LOSS' isn't clear? CHECKDB (Part 8): Can repair fix everything? (in fact, read the whole series) Ta da! Emergency mode repair (we didn’t have to resort to this one thank goodness)   Dave Just because I can…   [1] Names have been changed to protect the guilty. [2] I'm Batman. [3] And if I'm the coolest head in the room, you've got even bigger problems...

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  • MySQL Connect Only 10 Days Away - Focus on InnoDB Sessions

    - by Bertrand Matthelié
    Time flies and MySQL Connect is only 10 days away! You can check out the full program here as well as in the September edition of the MySQL newsletter. Mat recently blogged about the MySQL Cluster sessions you’ll have the opportunity to attend, and below are those focused on InnoDB. Remember you can plan your schedule with Schedule Builder. Saturday, 1.00 pm, Room Golden Gate 3: 10 Things You Should Know About InnoDB—Calvin Sun, Oracle InnoDB is the default storage engine for Oracle’s MySQL as of MySQL Release 5.5. It provides the standard ACID-compliant transactions, row-level locking, multiversion concurrency control, and referential integrity. InnoDB also implements several innovative technologies to improve its performance and reliability. This presentation gives a brief history of InnoDB; its main features; and some recent enhancements for better performance, scalability, and availability. Saturday, 5.30 pm, Room Golden Gate 4: Demystified MySQL/InnoDB Performance Tuning—Dimitri Kravtchuk, Oracle This session covers performance tuning with MySQL and the InnoDB storage engine for MySQL and explains the main improvements made in MySQL Release 5.5 and Release 5.6. Which setting for which workload? Which value will be better for my system? How can I avoid potential bottlenecks from the beginning? Do I need a purge thread? Is it true that InnoDB doesn't need thread concurrency anymore? These and many other questions are asked by DBAs and developers. Things are changing quickly and constantly, and there is no “silver bullet.” But understanding the configuration setting’s impact is already a huge step in performance improvement. Bring your ideas and problems to share them with others—the discussion is open, just moderated by a speaker. Sunday, 10.15 am, Room Golden Gate 4: Better Availability with InnoDB Online Operations—Calvin Sun, Oracle Many top Web properties rely on Oracle’s MySQL as a critical piece of infrastructure for serving millions of users. Database availability has become increasingly important. One way to enhance availability is to give users full access to the database during data definition language (DDL) operations. The online DDL operations in recent MySQL releases offer users the flexibility to perform schema changes while having full access to the database—that is, with minimal delay of operations on a table and without rebuilding the entire table. These enhancements provide better responsiveness and availability in busy production environments. This session covers these improvements in the InnoDB storage engine for MySQL for online DDL operations such as add index, drop foreign key, and rename column. Sunday, 11.45 am, Room Golden Gate 7: Developing High-Throughput Services with NoSQL APIs to InnoDB and MySQL Cluster—Andrew Morgan and John Duncan, Oracle Ever-increasing performance demands of Web-based services have generated significant interest in providing NoSQL access methods to MySQL (MySQL Cluster and the InnoDB storage engine of MySQL), enabling users to maintain all the advantages of their existing relational databases while providing blazing-fast performance for simple queries. Get the best of both worlds: persistence; consistency; rich SQL queries; high availability; scalability; and simple, flexible APIs and schemas for agile development. This session describes the memcached connectors and examines some use cases for how MySQL and memcached fit together in application architectures. It does the same for the newest MySQL Cluster native connector, an easy-to-use, fully asynchronous connector for Node.js. Sunday, 1.15 pm, Room Golden Gate 4: InnoDB Performance Tuning—Inaam Rana, Oracle The InnoDB storage engine has always been highly efficient and includes many unique architectural elements to ensure high performance and scalability. In MySQL 5.5 and MySQL 5.6, InnoDB includes many new features that take better advantage of recent advances in operating systems and hardware platforms than previous releases did. This session describes unique InnoDB architectural elements for performance, new features, and how to tune InnoDB to achieve better performance. Sunday, 4.15 pm, Room Golden Gate 3: InnoDB Compression for OLTP—Nizameddin Ordulu, Facebook and Inaam Rana, Oracle Data compression is an important capability of the InnoDB storage engine for Oracle’s MySQL. Compressed tables reduce the size of the database on disk, resulting in fewer reads and writes and better throughput by reducing the I/O workload. Facebook pushes the limit of InnoDB compression and has made several enhancements to InnoDB, making this technology ready for online transaction processing (OLTP). In this session, you will learn the fundamentals of InnoDB compression. You will also learn the enhancements the Facebook team has made to improve InnoDB compression, such as reducing compression failures, not logging compressed page images, and allowing changes of compression level. Not registered yet? You can still save US$ 300 over the on-site fee – Register Now!

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  • SQL SERVER – Not Possible – Delete From Multiple Table – Update Multiple Table in Single Statement

    - by pinaldave
    There are two questions which I get every single day multiple times. In my gmail, I have created standard canned reply for them. Let us see the questions here. I want to delete from multiple table in a single statement how will I do it? I want to update multiple table in a single statement how will I do it? The answer is – No, You cannot and you should not. SQL Server does not support deleting or updating from two tables in a single update. If you want to delete or update two different tables – you may want to write two different delete or update statements for it. This method has many issues – from the consistency of the data to SQL syntax. Now here is the real reason for this blog post – yesterday I was asked this question again and I replied my canned answer saying it is not possible and it should not be any way implemented that day. In the response to my reply I was pointed out to my own blog post where user suggested that I had previously mentioned this is possible and with demo example. Let us go over my conversation – you may find it interesting. Let us call the user DJ. DJ: Pinal, can we delete multiple table in a single statement or with single delete statement? Pinal: No, you cannot and you should not. DJ: Oh okey, if that is the case, why do you suggest to do that? Pinal: (baffled) I am not suggesting that. I am rather suggesting that it is not possible and it should not be possible. DJ: Hmm… but in that case why did you blog about it earlier? Pinal: (What?) No, I did not. I am pretty confident. DJ: Well, I am confident as well. You did. Pinal: In that case, it is my word against your word. Isn’t it? DJ: I have proof. Do you want to see it that you suggest it is possible? Pinal: Yes, I will be delighted too. (After 10 Minutes) DJ: Here are not one but two of your blog posts which talks about it - SQL SERVER – Curious Case of Disappearing Rows – ON UPDATE CASCADE and ON DELETE CASCADE – Part 1 of 2 SQL SERVER – Curious Case of Disappearing Rows – ON UPDATE CASCADE and ON DELETE CASCADE – T-SQL Example – Part 2 of 2 Pinal: Oh! DJ: I know I was correct. Pinal: Well, oh man, I did not mean there what you mean here. DJ: I did not understand can you explain it further. Pinal: Here we go. The example in the other blog is the example of the cascading delete or cascading update. I think you may want to understand the concept of the foreign keys and cascading update/delete. The concept of cascading exists to maintain data integrity. If there primary keys get deleted the update or delete reflects on the foreign key table to maintain the key integrity and data consistency. SQL Server follows ANSI Entry SQL with regard to referential integrity between PrimaryKey and ForeignKey columns which requires the inserting, updating, and deleting of data in related tables to be restricted to values that preserve the integrity. This is all together different concept than deleting multiple values in a single statement. When I hear that someone wants to delete or update multiple table in a single statement what I assume is something very similar to following. DELETE/UPDATE Table 1 (cols) Table 2 (cols) VALUES … which is not valid statement/syntax as well it is not ASNI standards as well. I guess, after this discussion with DJ, I realize I need to do a blog post so I can add the link to this blog post in my canned answer. Well, it was a fun conversation with DJ and I hope it the message is very clear now. Reference: Pinal Dave (http://blog.SQLAuthority.com) Filed under: PostADay, SQL, SQL Authority, SQL Joins, SQL Query, SQL Server, SQL Tips and Tricks, T SQL, Technology

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  • SQL SERVER – Curious Case of Disappearing Rows – ON UPDATE CASCADE and ON DELETE CASCADE – Part 1 of 2

    - by pinaldave
    Social media has created an Always Connected World for us. Recently I enrolled myself to learn new technologies as a student. I had decided to focus on learning and decided not to stay connected on the internet while I am in the learning session. On the second day of the event after the learning was over, I noticed lots of notification from my friend on my various social media handle. He had connected with me on Twitter, Facebook, Google+, LinkedIn, YouTube as well SMS, WhatsApp on the phone, Skype messages and not to forget with a few emails. I right away called him up. The problem was very unique – let us hear the problem in his own words. “Pinal – we are in big trouble we are not able to figure out what is going on. Our product details table is continuously loosing rows. Lots of rows have disappeared since morning and we are unable to find why the rows are getting deleted. We have made sure that there is no DELETE command executed on the table as well. The matter of the fact, we have removed every single place the code which is referencing the table. We have done so many crazy things out of desperation but no luck. The rows are continuously deleted in a random pattern. Do you think we have problems with intrusion or virus?” After describing the problems he had pasted few rants about why I was not available during the day. I think it will be not smart to post those exact words here (due to many reasons). Well, my immediate reaction was to get online with him. His problem was unique to him and his team was all out to fix the issue since morning. As he said he has done quite a lot out in desperation. I started asking questions from audit, policy management and profiling the data. Very soon I realize that I think this problem was not as advanced as it looked. There was no intrusion, SQL Injection or virus issue. Well, long story short first - It was a very simple issue of foreign key created with ON UPDATE CASCADE and ON DELETE CASCADE.  CASCADE allows deletions or updates of key values to cascade through the tables defined to have foreign key relationships that can be traced back to the table on which the modification is performed. ON DELETE CASCADE specifies that if an attempt is made to delete a row with a key referenced by foreign keys in existing rows in other tables, all rows containing those foreign keys are also deleted. ON UPDATE CASCADE specifies that if an attempt is made to update a key value in a row, where the key value is referenced by foreign keys in existing rows in other tables, all of the foreign key values are also updated to the new value specified for the key. (Reference: BOL) In simple words – due to ON DELETE CASCASE whenever is specified when the data from Table A is deleted and if it is referenced in another table using foreign key it will be deleted as well. In my friend’s case, they had two tables, Products and ProductDetails. They had created foreign key referential integrity of the product id between the table. Now the as fall was up they were updating their catalogue. When they were updating the catalogue they were deleting products which are no more available. As the changes were cascading the corresponding rows were also deleted from another table. This is CORRECT. The matter of the fact, there is no error or anything and SQL Server is behaving how it should be behaving. The problem was in the understanding and inappropriate implementations of business logic.  What they needed was Product Master Table, Current Product Catalogue, and Product Order Details History tables. However, they were using only two tables and without proper understanding the relation between them was build using foreign keys. If there were only two table, they should have used soft delete which will not actually delete the record but just hide it from the original product table. This workaround could have got them saved from cascading delete issues. I will be writing a detailed post on the design implications etc in my future post as in above three lines I cannot cover every issue related to designing and it is also not the scope of the blog post. More about designing in future blog posts. Once they learn their mistake, they were happy as there was no intrusion but trust me sometime we are our own enemy and this is a great example of it. In tomorrow’s blog post we will go over their code and workarounds. Feel free to share your opinions, experiences and comments. Reference: Pinal Dave (http://blog.sqlauthority.com) Filed under: PostADay, SQL, SQL Authority, SQL Query, SQL Server, SQL Tips and Tricks, T SQL, Technology

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  • iPhone OpenGL ES: How do I use gravity vector to correctly transform scene for augmented reality

    - by gpdawson
    I'm trying figure out how to get an OpenGL specified object to be displayed correctly according to the device orientation (ie. according to the gravity vector from the accelerometer, and heading from compass). The GLGravity sample project has an example which is almost like this (despite ignoring heading), but it has some glitches. For example, the teapot jumps 180deg as the device viewing angle crosses the horizon, and it also rotates spuriously if you tilt the device from portrait into landscape. This is fine for the context of this app, as it just shows off an object and it doesn't matter that it does these things. But it means that the code just doesn't work when you attempt to emulate real life viewing of an OpenGL object according to the device's orientation. What happens is that it almost works, but the heading rotation you apply from the compass gets "corrupted" by the spurious additional rotations seen in the GLGravity example project. Can anyone provide sample code that shows how to adjust correctly for the device orientation (ie. gravity vector), or to fix the GLGravity example so that it doesn't include spurious heading changes? //Clear matrix to be used to rotate from the current referential to one based on the gravity vector bzero(matrix, sizeof(matrix)); matrix[3][3] = 1.0; //Setup first matrix column as gravity vector matrix[0][0] = accel[0] / length; matrix[0][1] = accel[1] / length; matrix[0][2] = accel[2] / length; //Setup second matrix column as an arbitrary vector in the plane perpendicular to the gravity vector {Gx, Gy, Gz} defined by by the equation "Gx * x + Gy * y + Gz * z = 0" in which we arbitrarily set x=0 and y=1 matrix[1][0] = 0.0; matrix[1][1] = 1.0; matrix[1][2] = -accel[1] / accel[2]; length = sqrtf(matrix[1][0] * matrix[1][0] + matrix[1][1] * matrix[1][1] + matrix[1][2] * matrix[1][2]); matrix[1][0] /= length; matrix[1][1] /= length; matrix[1][2] /= length; //Setup third matrix column as the cross product of the first two matrix[2][0] = matrix[0][1] * matrix[1][2] - matrix[0][2] * matrix[1][1]; matrix[2][1] = matrix[1][0] * matrix[0][2] - matrix[1][2] * matrix[0][0]; matrix[2][2] = matrix[0][0] * matrix[1][1] - matrix[0][1] * matrix[1][0]; //Finally load matrix glMultMatrixf((GLfloat*)matrix);

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  • How do I use the gravity vector to correctly transform scene for augmented reality?

    - by gpdawson
    I'm trying figure out how to get an OpenGL specified object to be displayed correctly according to the device orientation (ie. according to the gravity vector from the accelerometer, and heading from compass). The GLGravity sample project has an example which is almost like this (despite ignoring heading), but it has some glitches. For example, the teapot jumps 180deg as the device viewing angle crosses the horizon, and it also rotates spuriously if you tilt the device from portrait into landscape. This is fine for the context of this app, as it just shows off an object and it doesn't matter that it does these things. But it means that the code just doesn't work when you attempt to emulate real life viewing of an OpenGL object according to the device's orientation. What happens is that it almost works, but the heading rotation you apply from the compass gets "corrupted" by the spurious additional rotations seen in the GLGravity example project. Can anyone provide sample code that shows how to adjust correctly for the device orientation (ie. gravity vector), or to fix the GLGravity example so that it doesn't include spurious heading changes? //Clear matrix to be used to rotate from the current referential to one based on the gravity vector bzero(matrix, sizeof(matrix)); matrix[3][3] = 1.0; //Setup first matrix column as gravity vector matrix[0][0] = accel[0] / length; matrix[0][1] = accel[1] / length; matrix[0][2] = accel[2] / length; //Setup second matrix column as an arbitrary vector in the plane perpendicular to the gravity vector {Gx, Gy, Gz} defined by by the equation "Gx * x + Gy * y + Gz * z = 0" in which we arbitrarily set x=0 and y=1 matrix[1][0] = 0.0; matrix[1][1] = 1.0; matrix[1][2] = -accel[1] / accel[2]; length = sqrtf(matrix[1][0] * matrix[1][0] + matrix[1][1] * matrix[1][1] + matrix[1][2] * matrix[1][2]); matrix[1][0] /= length; matrix[1][1] /= length; matrix[1][2] /= length; //Setup third matrix column as the cross product of the first two matrix[2][0] = matrix[0][1] * matrix[1][2] - matrix[0][2] * matrix[1][1]; matrix[2][1] = matrix[1][0] * matrix[0][2] - matrix[1][2] * matrix[0][0]; matrix[2][2] = matrix[0][0] * matrix[1][1] - matrix[0][1] * matrix[1][0]; //Finally load matrix glMultMatrixf((GLfloat*)matrix);

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  • Is Delete cascade possible in ravendb

    - by user1811801
    Still just a starter in ravendb. I have a doubt whether raven db supports some kind of referential integrity. Here is my doubt and work.. I have document type screens as below public class Screens { public String Id { get; set; } public String ScreenName { get; set; } } And Another document named RightsDeclaration as below public class RightsDeclaration { public RightsDeclaration() { _screenrights = new List<ScreenRight>(); } public String Id { get; set; }// Role Name List<ScreenRight> _screenrights; public List<ScreenRight> ScreenRights { get { return _screenrights; } set { _screenrights = value; } } } Now the screen rights class looks like below with the screen name field as below public class ScreenRight : { public String ScreenName { get; set; } public Boolean Create { get; set; } public Boolean Read { get; set; } public Boolean Update { get; set; } public Boolean Delete { get; set; } public Boolean Approve { get; set; } public Boolean Access { get; set; } public Boolean Print { get; set; } public Boolean Email { get; set; } } Now first i will create some list of screens and then i assign rights for each role with mentioning what is the screen name and list of rights. up to this point everything goes fine. Now in a scenario where if i would delete the screen name in screens class but then the screen rights for that screen still exists in the rights declaration. is it possible to delete the corresponding screen rights from userrights document too? if so please mention the query or idea to do the above.. Thanks in advance..

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  • SQL Server architecture guidance

    - by Liam
    Hi, We are designing a new version of our existing product on a new schema. Its an internal web application with possibly 100 concurrent users (max)This will run on a SQL Server 2008 database. On of the discussion items recently is whether we should have a single database of split the database for performance reasons across 2 separate databases. The database could grow anywhere from 50-100GB over 5 years. We are Developers and not DBAs so it would be nice to get some general guidance. [I know the answer is not simple as it depends on the schema, archiving policy, amount of data etc. ] Option 1 Single Main Database [This is my preferred option]. The plan would be to have all the tables in a single database and possibly to use file groups and partitioning to separate the data if required across multiple disks. [Use schema if appropriate]. This should deal with the performance concerns One of the comments wrt this was that the a single server instance would still be processing this data so there would still be a processing bottle neck. For reporting we could have a separate reporting DB but this is still being discussed. Option 2 Split the database into 2 separate databases DB1 - Customers, Accounts, Customer resources etc DB2 - This would contain the bulk of the data [i.e. Vehicle tracking data, financial transaction tables etc]. These tables would typically contain a lot of data. [It could reside on a separate server if required] This plan would involve keeping the main data in a smaller database [DB1] and retaining the [mainly] read only transaction type data in a separate DB [DB2]. The UI would mainly read from DB1 and thus be more responsive. [I'm aware that this option makes it harder for Referential Integrity to be enforced.] Points for consideration As we are at the design stage we can at least make proper use of indexes to deal performance issues so thats why option 1 to me is attractive and its more of a standard approach. For both options we are considering implementing an archiving database. Apologies for the long Question. In summary the question is 1 DB or 2? Thanks in advance, Liam

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