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• Database - Designing an "Events" Table

  - by Alix Axel

  After reading the tips from this great Nettuts+ article I've come up with a table schema that would separate highly volatile data from other tables subjected to heavy reads and at the same time lower the number of tables needed in the whole database schema, however I'm not sure if this is a good idea since it doesn't follow the rules of normalization and I would like to hear your advice, here is the general idea: I've four types of users modeled in a Class Table Inheritance structure, in the main "user" table I store data common to all the users (id, username, password, several flags, ...) along with some TIMESTAMP fields (date_created, date_updated, date_activated, date_lastLogin, ...). To quote the tip #16 from the Nettuts+ article mentioned above: Example 2: You have a “last_login” field in your table. It updates every time a user logs in to the website. But every update on a table causes the query cache for that table to be flushed. You can put that field into another table to keep updates to your users table to a minimum. Now it gets even trickier, I need to keep track of some user statistics like how many unique times a user profile was seen how many unique times a ad from a specific type of user was clicked how many unique times a post from a specific type of user was seen and so on... In my fully normalized database this adds up to about 8 to 10 additional tables, it's not a lot but I would like to keep things simple if I could, so I've come up with the following "events" table: |------|----------------|----------------|--------------|-----------| | ID | TABLE | EVENT | DATE | IP | |------|----------------|----------------|--------------|-----------| | 1 | user | login | 201004190030 | 127.0.0.1 | |------|----------------|----------------|--------------|-----------| | 1 | user | login | 201004190230 | 127.0.0.1 | |------|----------------|----------------|--------------|-----------| | 2 | user | created | 201004190031 | 127.0.0.2 | |------|----------------|----------------|--------------|-----------| | 2 | user | activated | 201004190234 | 127.0.0.2 | |------|----------------|----------------|--------------|-----------| | 2 | user | approved | 201004190930 | 217.0.0.1 | |------|----------------|----------------|--------------|-----------| | 2 | user | login | 201004191200 | 127.0.0.2 | |------|----------------|----------------|--------------|-----------| | 15 | user_ads | created | 201004191230 | 127.0.0.1 | |------|----------------|----------------|--------------|-----------| | 15 | user_ads | impressed | 201004191231 | 127.0.0.2 | |------|----------------|----------------|--------------|-----------| | 15 | user_ads | clicked | 201004191231 | 127.0.0.2 | |------|----------------|----------------|--------------|-----------| | 15 | user_ads | clicked | 201004191231 | 127.0.0.2 | |------|----------------|----------------|--------------|-----------| | 15 | user_ads | clicked | 201004191231 | 127.0.0.2 | |------|----------------|----------------|--------------|-----------| | 15 | user_ads | clicked | 201004191231 | 127.0.0.2 | |------|----------------|----------------|--------------|-----------| | 15 | user_ads | clicked | 201004191231 | 127.0.0.2 | |------|----------------|----------------|--------------|-----------| | 2 | user | blocked | 201004200319 | 217.0.0.1 | |------|----------------|----------------|--------------|-----------| | 2 | user | deleted | 201004200320 | 217.0.0.1 | |------|----------------|----------------|--------------|-----------| Basically the ID refers to the primary key (id) field in the TABLE table, I believe the rest should be pretty straightforward. One thing that I've come to like in this design is that I can keep track of all the user logins instead of just the last one, and thus generate some interesting metrics with that data. Due to the nature of the events table I also thought of making some optimizations, such as: #9: Since there is only a finite number of tables and a finite (and predetermined) number of events, the TABLE and EVENTS columns could be setup as ENUMs instead of VARCHARs to save some space. #14: Store IPs as UNSIGNED INT with INET_ATON() instead of VARCHARs. Store DATEs as TIMESTAMPs instead of DATETIMEs. Use the ARCHIVE (or the CSV?) engine instead of InnoDB / MyISAM. Overall, each event would only consume 14 bytes which is okay for my traffic I guess. Pros: Ability to store more detailed data (such as logins). No need to design (and code for) almost a dozen additional tables (dates and statistics). Reduces a few columns per table and keeps volatile data separated. Cons: Non-relational (still not as bad as EAV): SELECT * FROM events WHERE id = 2 AND table = 'user' ORDER BY date DESC(); 6 bytes overhead per event (ID, TABLE and EVENT). I'm more inclined to go with this approach since the pros seem to far outweigh the cons, but I'm still a little bit reluctant.. Am I missing something? What are your thoughts on this? Thanks!

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• Oracle Database Third Party Model Import and Scoring - Poll

  - by [email protected]

  We in the Oracle Data Mining Technologies group are interested in your needs for third party model import. Are you interested in importing SAS, SPSS, R, etc. analytic models into Oracle for in-database scoring? Thank you for taking a minute to participate in this quick poll.Click here to take the poll.

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• Ha a hutés nem elég a gépteremben: Sun Cooling Door a Database Machine-hoz

  - by Fekete Zoltán

  A Database Machine hatalmas teljesítménye miatt általában jóval kevesebb hutésre van szükség, mintha egy külön high-end servert és külön high-end storage-ot hutenénk! Ha viszont a géptermünk maradék hutési kapacitása nem elegendo, és nem elégszünk meg a "hagyományos mosóporral", akkor újabb hutési trükkre van szükség. Erre kínálnak megoldást a Sun Cooling Door modellek, például az 5200-as és az 5600-as modellek.

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• Adatlap az Exadata, Database Machine supporthoz

  - by Fekete Zoltán

  Letöltheto és megtekintheto, sot elolvasható :) a COMPLETE SUPPORT SERVICES FOR ORACLE EXADATA dokumentum, amely részletesen leírja, milyen trméktámogatási lehetoségeket lehet igénybe venni egy Database Machine megoldáshoz. Az Exadata termékcsalád elemei mind tranzakciós rendszerek mind adattárházak adatbázisának futtatásához és adatbázisok egy közös szerveren muködtetéséhez nyújtanak optimális, nagy teljesítményu platformot.

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• Details on Oracle's Primavera P6 Reporting Database R2

  - by mark.kromer

  Below is a graphic screenshot of our detailed announcement for the new Oracle data warehouse product for Primavera P6 called P6 Reporting Database R2. This DW product includes the ETL, data warehouse star schemas and ODS that you'll need to build an enterprise reporting solution for your projects & portfolios. This product is included on a restricted license basis with the new Primavera P6 Analytics R1 product from Oracle because those Analytics are built in OBIEE based on this data warehouse product.

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• SQL SERVER – Creating All New Database with Full Recovery Model

  - by pinaldave

  Sometimes, complex problems have very simple solutions. Let us see the following email which I received recently. “Hi Pinal, In our system when we create new database, by default, they are all created with the Simple Recovery Model. We have to manually change the recovery model after we create the database. We used the following simple T-SQL code: CREATE DATABASE dbname. We are very frustrated with this situation. We want all our databases to have the Full Recovery Model option by default. We are considering the following methods; please suggest the most efficient one among them. 1) Creating a Policy; when it is violated, the database model can be fixed 2) Triggers at Server Level 3) Automated Job which goes through all the databases and checks their recovery model; if the DBA has not changed the model, then the job will list the Databases and change their recovery model Also, we have a situation where we need a database in the Simple Recovery Model as well – how to white list them? Please suggest the best method.” Indeed, an interesting email! The answer to their question, i.e., which is the best method to fit their needs (white list, default, etc)? It will be NONE of the above. Here is the solution in one line and also the easiest way: Just go to your Model database: Path in SSMS >> Databases > System Databases >> model >> Right Click Properties >> Options >> Recovery Model - Select Full from dropdown. Every newly created database takes its base template from the Model Database. If you create a custom SP in the Model Database, when you create a new database, it will automatically exist in that database. Any database that was already created before making changes in the Model Database will not be affected at all. Creating Policy is also a good method, and I will blog about this in a separate blog post, but looking at current specifications of the reader, I think the Model Database should be modified to have a Full Recovery Option. While writing this blog post, I remembered my another blog post where the model database log file was growing drastically even though there were no transactions SQL SERVER – Log File Growing for Model Database – model Database Log File Grew Too Big. NOTE: Please do not touch the Model Database unnecessary. It is a strict “No.” If you want to create an object that you need in all the databases, then instead of creating it in model database, I suggest that you create a new database called maintenance and create the object there. Reference: Pinal Dave (http://blog.SQLAuthority.com) Filed under: PostADay, Readers Question, SQL, SQL Authority, SQL Query, SQL Server, SQL Tips and Tricks, T SQL, Technology

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• Oracle Database 12 c New Partition Maintenance Features by Gwen Lazenby

  - by hamsun

  One of my favourite new features in Oracle Database 12c is the ability to perform partition maintenance operations on multiple partitions. This means we can now add, drop, truncate and merge multiple partitions in one operation, and can split a single partition into more than two partitions also in just one command. This would certainly have made my life slightly easier had it been available when I administered a data warehouse at Oracle 9i. To demonstrate this new functionality and syntax, I am going to create two tables, ORDERS and ORDERS_ITEMS which have a parent-child relationship. ORDERS is to be partitioned using range partitioning on the ORDER_DATE column, and ORDER_ITEMS is going to partitioned using reference partitioning and its foreign key relationship with the ORDERS table. This form of partitioning was a new feature in 11g and means that any partition maintenance operations performed on the ORDERS table will also take place on the ORDER_ITEMS table as well. First create the ORDERS table - SQL CREATE TABLE orders ( order_id NUMBER(12), order_date TIMESTAMP, order_mode VARCHAR2(8), customer_id NUMBER(6), order_status NUMBER(2), order_total NUMBER(8,2), sales_rep_id NUMBER(6), promotion_id NUMBER(6), CONSTRAINT orders_pk PRIMARY KEY(order_id) ) PARTITION BY RANGE(order_date) (PARTITION Q1_2007 VALUES LESS THAN (TO_DATE('01-APR-2007','DD-MON-YYYY')), PARTITION Q2_2007 VALUES LESS THAN (TO_DATE('01-JUL-2007','DD-MON-YYYY')), PARTITION Q3_2007 VALUES LESS THAN (TO_DATE('01-OCT-2007','DD-MON-YYYY')), PARTITION Q4_2007 VALUES LESS THAN (TO_DATE('01-JAN-2008','DD-MON-YYYY')) ); Table created. Now the ORDER_ITEMS table SQL CREATE TABLE order_items ( order_id NUMBER(12) NOT NULL, line_item_id NUMBER(3) NOT NULL, product_id NUMBER(6) NOT NULL, unit_price NUMBER(8,2), quantity NUMBER(8), CONSTRAINT order_items_fk FOREIGN KEY(order_id) REFERENCES orders(order_id) on delete cascade) PARTITION BY REFERENCE(order_items_fk) tablespace example; Table created. Now look at DBA_TAB_PARTITIONS to get details of what partitions we have in the two tables – SQL select table_name,partition_name, partition_position position, high_value from dba_tab_partitions where table_owner='SH' and table_name like 'ORDER_%' order by partition_position, table_name; TABLE_NAME PARTITION_NAME POSITION HIGH_VALUE -------------- --------------- -------- ------------------------- ORDERS Q1_2007 1 TIMESTAMP' 2007-04-01 00:00:00' ORDER_ITEMS Q1_2007 1 ORDERS Q2_2007 2 TIMESTAMP' 2007-07-01 00:00:00' ORDER_ITEMS Q2_2007 2 ORDERS Q3_2007 3 TIMESTAMP' 2007-10-01 00:00:00' ORDER_ITEMS Q3_2007 3 ORDERS Q4_2007 4 TIMESTAMP' 2008-01-01 00:00:00' ORDER_ITEMS Q4_2007 4 Just as an aside it is also now possible in 12c to use interval partitioning on reference partitioned tables. In 11g it was not possible to combine these two new partitioning features. For our first example of the new 12cfunctionality, let us add all the partitions necessary for 2008 to the tables using one command. Notice that the partition specification part of the add command is identical in format to the partition specification part of the create command as shown above - SQL alter table orders add PARTITION Q1_2008 VALUES LESS THAN (TO_DATE('01-APR-2008','DD-MON-YYYY')), PARTITION Q2_2008 VALUES LESS THAN (TO_DATE('01-JUL-2008','DD-MON-YYYY')), PARTITION Q3_2008 VALUES LESS THAN (TO_DATE('01-OCT-2008','DD-MON-YYYY')), PARTITION Q4_2008 VALUES LESS THAN (TO_DATE('01-JAN-2009','DD-MON-YYYY')); Table altered. Now look at DBA_TAB_PARTITIONS and we can see that the 4 new partitions have been added to both tables – SQL select table_name,partition_name, partition_position position, high_value from dba_tab_partitions where table_owner='SH' and table_name like 'ORDER_%' order by partition_position, table_name; TABLE_NAME PARTITION_NAME POSITION HIGH_VALUE -------------- --------------- -------- ------------------------- ORDERS Q1_2007 1 TIMESTAMP' 2007-04-01 00:00:00' ORDER_ITEMS Q1_2007 1 ORDERS Q2_2007 2 TIMESTAMP' 2007-07-01 00:00:00' ORDER_ITEMS Q2_2007 2 ORDERS Q3_2007 3 TIMESTAMP' 2007-10-01 00:00:00' ORDER_ITEMS Q3_2007 3 ORDERS Q4_2007 4 TIMESTAMP' 2008-01-01 00:00:00' ORDER_ITEMS Q4_2007 4 ORDERS Q1_2008 5 TIMESTAMP' 2008-04-01 00:00:00' ORDER_ITEMS Q1_2008 5 ORDERS Q2_2008 6 TIMESTAMP' 2008-07-01 00:00:00' ORDER_ITEM Q2_2008 6 ORDERS Q3_2008 7 TIMESTAMP' 2008-10-01 00:00:00' ORDER_ITEMS Q3_2008 7 ORDERS Q4_2008 8 TIMESTAMP' 2009-01-01 00:00:00' ORDER_ITEMS Q4_2008 8 Next, we can drop or truncate multiple partitions by giving a comma separated list in the alter table command. Note the use of the plural ‘partitions’ in the command as opposed to the singular ‘partition’ prior to 12c– SQL alter table orders drop partitions Q3_2008,Q2_2008,Q1_2008; Table altered. Now look at DBA_TAB_PARTITIONS and we can see that the 3 partitions have been dropped in both the two tables – TABLE_NAME PARTITION_NAME POSITION HIGH_VALUE -------------- --------------- -------- ------------------------- ORDERS Q1_2007 1 TIMESTAMP' 2007-04-01 00:00:00' ORDER_ITEMS Q1_2007 1 ORDERS Q2_2007 2 TIMESTAMP' 2007-07-01 00:00:00' ORDER_ITEMS Q2_2007 2 ORDERS Q3_2007 3 TIMESTAMP' 2007-10-01 00:00:00' ORDER_ITEMS Q3_2007 3 ORDERS Q4_2007 4 TIMESTAMP' 2008-01-01 00:00:00' ORDER_ITEMS Q4_2007 4 ORDERS Q4_2008 5 TIMESTAMP' 2009-01-01 00:00:00' ORDER_ITEMS Q4_2008 5 Now let us merge all the 2007 partitions together to form one single partition – SQL alter table orders merge partitions Q1_2005, Q2_2005, Q3_2005, Q4_2005 into partition Y_2007; Table altered. TABLE_NAME PARTITION_NAME POSITION HIGH_VALUE -------------- --------------- -------- ------------------------- ORDERS Y_2007 1 TIMESTAMP' 2008-01-01 00:00:00' ORDER_ITEMS Y_2007 1 ORDERS Q4_2008 2 TIMESTAMP' 2009-01-01 00:00:00' ORDER_ITEMS Q4_2008 2 Splitting partitions is a slightly more involved. In the case of range partitioning one of the new partitions must have no high value defined, and in list partitioning one of the new partitions must have no list of values defined. I call these partitions the ‘everything else’ partitions, and will contain any rows contained in the original partition that are not contained in the any of the other new partitions. For example, let us split the Y_2007 partition back into 4 quarterly partitions – SQL alter table orders split partition Y_2007 into (PARTITION Q1_2007 VALUES LESS THAN (TO_DATE('01-APR-2007','DD-MON-YYYY')), PARTITION Q2_2007 VALUES LESS THAN (TO_DATE('01-JUL-2007','DD-MON-YYYY')), PARTITION Q3_2007 VALUES LESS THAN (TO_DATE('01-OCT-2007','DD-MON-YYYY')), PARTITION Q4_2007); Now look at DBA_TAB_PARTITIONS to get details of the new partitions – TABLE_NAME PARTITION_NAME POSITION HIGH_VALUE -------------- --------------- -------- ------------------------- ORDERS Q1_2007 1 TIMESTAMP' 2007-04-01 00:00:00' ORDER_ITEMS Q1_2007 1 ORDERS Q2_2007 2 TIMESTAMP' 2007-07-01 00:00:00' ORDER_ITEMS Q2_2007 2 ORDERS Q3_2007 3 TIMESTAMP' 2007-10-01 00:00:00' ORDER_ITEMS Q3_2007 3 ORDERS Q4_2007 4 TIMESTAMP' 2008-01-01 00:00:00' ORDER_ITEMS Q4_2007 4 ORDERS Q4_2008 5 TIMESTAMP' 2009-01-01 00:00:00' ORDER_ITEMS Q4_2008 5 Partition Q4_2007 has a high value equal to the high value of the original Y_2007 partition, and so has inherited its upper boundary from the partition that was split. As for a list partitioning example let look at the following another table, SALES_PAR_LIST, which has 2 partitions, Americas and Europe and a partitioning key of country_name. SQL select table_name,partition_name, high_value from dba_tab_partitions where table_owner='SH' and table_name = 'SALES_PAR_LIST'; TABLE_NAME PARTITION_NAME HIGH_VALUE -------------- --------------- ----------------------------- SALES_PAR_LIST AMERICAS 'Argentina', 'Canada', 'Peru', 'USA', 'Honduras', 'Brazil', 'Nicaragua' SALES_PAR_LIST EUROPE 'France', 'Spain', 'Ireland', 'Germany', 'Belgium', 'Portugal', 'Denmark' Now split the Americas partition into 3 partitions – SQL alter table sales_par_list split partition americas into (partition south_america values ('Argentina','Peru','Brazil'), partition north_america values('Canada','USA'), partition central_america); Table altered. Note that no list of values was given for the ‘Central America’ partition. However it should have inherited any values in the original ‘Americas’ partition that were not assigned to either the ‘North America’ or ‘South America’ partitions. We can confirm this by looking at the DBA_TAB_PARTITIONS view. SQL select table_name,partition_name, high_value from dba_tab_partitions where table_owner='SH' and table_name = 'SALES_PAR_LIST'; TABLE_NAME PARTITION_NAME HIGH_VALUE --------------- --------------- -------------------------------- SALES_PAR_LIST SOUTH_AMERICA 'Argentina', 'Peru', 'Brazil' SALES_PAR_LIST NORTH_AMERICA 'Canada', 'USA' SALES_PAR_LIST CENTRAL_AMERICA 'Honduras', 'Nicaragua' SALES_PAR_LIST EUROPE 'France', 'Spain', 'Ireland', 'Germany', 'Belgium', 'Portugal', 'Denmark' In conclusion, I hope that DBA’s whose work involves maintaining partitions will find the operations a bit more straight forward to carry out once they have upgraded to Oracle Database 12c. Gwen Lazenby is a Principal Training Consultant at Oracle. She is part of Oracle University's Core Technology delivery team based in the UK, teaching Database Administration and Linux courses. Her specialist topics include using Oracle Partitioning and Parallelism in Data Warehouse environments, as well as Oracle Spatial and RMAN.

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• Should experienced programmers know database queries?

  - by Shamim Hafiz

  There are so many programmers out there who are also an expert at Query writing and Database design. Should this be a core requirement to be an expert programmer or software engineer? Though there are lots of similarities in the way queries and codes are developed, my personal opinion is, Queries seem to have a different Structure than Code and it can be tough to Master both simultaneously due to the different approaches.

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• Statistical Sampling for Verifying Database Backups

  A DBA's huge workload can start to threaten best practices for data backup and recovery, but ingenuity, and an eye for a good tactic, can usually find a way. For Tom, the revelation about a solution came from eating crabs. Statistical sampling can be brought to bear to minimise the risk of faliure of an emergency database restore.

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• Get Info From Database, or Build Inferred Info?

  - by Zaemz

  Does it make more sense to store and retrieve properties or information directly related to an item in a database, or, say in such a case that a product's ID could describe information about it, should the information be gathered from that? Example: Item SKU -- 4HBU12 4 - is the number of motors H - the voltage B - the color, blue U - the model 12 - the length Should I store those individual attributes as well as the SKU, or should I store only the SKU and build the attributes from it?

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• Configurable tables in sql database

  - by dot

  I have the following tables in my database: Config Table: ====================================== Start_Range | End Range | Config_id 10 | 15 | 1 ====================================== Available_UserIDs ========================== ID | UserID | Used_YN | 1 | 10 | t | 1 | 11 | f | 1 | 12 | f | 1 | 13 | f | 1 | 14 | f | 1 | 15 | f | ========================== Users ========================== UserId | FName | LName | 10 |John | Doe | ========================== This is used in a reservation system of sorts... which lets an administrator specify a range of numbers that will be assigned to users in the config table. Once the range has been defined, the system then populates the Available_userIDs table with all the numbers in between the range, and sets the Used_YN flag to false As users sign up, they grab the next user_id number that's not in use... and reserve it. Then the system adds a record to the Users table. Once the admin has specified a range, it is possible that they can change it. For example, they can start with 10-15... and then when the range is used up, they should be able to specify another range like 16 - 99. I've put a unique constraint on the Available_UserIDs table, as well as on the Users table - to ensure that UserIds can't be duplicated. My questions are as follows: What's the best way to prevent the admins from using a range that's already in use? I thought of the following options: -- check either the Users table to see if the start range or ending range numbers are being used. If they are, assume that all the numbers in between are in use too, and reject the range. -- let them specify whatever they want, try to populate the Available_UserIDs table. If there are duplicates, just ignore that specific error message from the database and continue on. How do I find gaps in the number ranges? For example, if they specify 10-15, and then 20-25, it'd be nice to be able to somehow suggest on my web page that 16-19 is currently available. I found this article: http://stackoverflow.com/questions/1312101/how-to-find-a-gap-in-running-counter-with-sql But it only seems to return the first available number... so in my example above, it would only return the number 16. I'm sure there's a simpler way to do things that I'm overlooking!

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• Database ERD design: 2 types user in one table

  - by Giskin Leow

  I have read this (Database design: 3 types of users, separate or one table?) I decided to put admin and normal user in one table since the attributes are similar: fullname, address, phone, email, gender ... Then I want to draw ERD, suddenly my mind pop out a question. How to draw? Customer make appointment and admin approve appointment. now only two tables, and admin, customer in same table. Help.

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• Oracle Database Appliance Product Development Webinar Series – Fridays

  - by Cinzia Mascanzoni

  Join Sohan DeMel, VP Product Strategy and Business Development, every Friday to hear about the latest tools and best practices designed to help you close more business with the Oracle Database Appliance. Bookmark this OPN page to add upcoming calls to your calendar, as well as playback the replays from all of our past sessions including Best Practices, Customer Wins, and Use Cases.

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• How to connect to database on remote server

  - by user137263

  Where there is VPN to remote server and then access to the database via local network interface, how can one establish a remote link between one's computer (with a programme such as Visual Studio 2010) and SQL Server (e.g. 2008 R2) ? Any attempts to create a direct link to the SQL Server are blocked. Whilst the SQL Server can be configured to allow external access, this provides its own host of problems. Any help would be much appreciated.

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• Oracle Database Appliance Product Development Webinar Series – Fridays

  - by Cinzia Mascanzoni

  On November 2nd, Sohan DeMel, VP Product Strategy and Business Development, will be kicking off the next round of topics in this valuable webinar series. Encourage your partners to attend to learn about the latest tools and best practices to close more business with the Oracle Database Appliance. Click here for more information.

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• Database Design for a double entry accounting system

  - by Khou

  Should journal entries be recorded in a database design? In the real world it makes sense to keep a daily entry book, then later transfer the daily entry book into double entry accounts. but in the computerized version, doing this produces duplicate records and that doesn't quite make sense? ???? What i mean is 1) user enter details , it gets recorded (this would be called the journalbook in real life) 2) the software does all the double entry accounting then references the journalbook and splits up the transaction into the double entry accounting system.

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• Database theory - relationship between two tables

  - by iansinke

  I have a database with two tables - let's call them Foo and Bar. Each foo may be related to any number of bars, and each bar may be related to any number of foos. I want to be able to retrieve, with one query, the foos that are associated with a certain bar, and the bars that are associated with a certain foo. My question is, what is the best way of recording these relationships? Should I have a separate table with records of each relationship (e.g. two columns, foo and bar)? Should the foo table have a column for a list of bars, and vice versa? Is there another option that I'm overlooking? I'm using SQL Server, if that makes a difference.

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• Database design in blogging systems

  - by Peter

  As a learning exercise I'm trying to put myself a blogging system. The goal is to code something that will let me create multiple blogs, like blogger.com or wordpress.com, but much simplified. I would like to ask you, what do you think is best database design for this type of script. Is it better to have one big table, containing posts from all blogs of all users (like friendfeed) or would it be better to create separate table for each blog's posts? Big thanks in advance for your help, Peter.

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• Making a DateTime field in a database automatic?

  - by Mike

  I'm putting together a simple test database to learn MVC with. I want to add a DateTime field to show when the record was CREATED. ID = int Name = Char DateCreated = (dateTime, DateTime2..?) I have a feeling that this type of DateTime capture can be done automatically - but that's all I have, a feeling. Can it be done? And if so how? While we're on the subject: if I wanted to include another field that captured the DateTime of when the record was LAST UPDATED how would I do that. I'm hoping to not do this manually. Many thanks Mike

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• Making a DateTime field in SQLExpress database?

  - by Mike

  I'm putting together a simple test database to learn MVC with. I want to add a DateTime field to show when the record was CREATED. ID = int Name = Char DateCreated = (dateTime, DateTime2..?) I have a feeling that this type of DateTime capture can be done automatically - but that's all I have, a feeling. Can it be done? And if so how? While we're on the subject: if I wanted to include another field that captured the DateTime of when the record was LAST UPDATED how would I do that. I'm hoping to not do this manually. Many thanks Mike

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• mySQL and general database normalization question

  - by Sinan

  I have question about normalization. Suppose I have an applications dealing with songs. First I thought about doing like this: Songs Table: id | song_title | album_id | publisher_id | artist_id Albums Table: id | album_title | etc... Publishers Table: id | publisher_name | etc... Artists Tale: id | artist_name | etc... Then as I think about normalization stuff. I thought I should get rid of "album_id, publisher_id, and artist_id in songs table and put them in intermediate tables like this. Table song_album: song_id, album_id Table song_publisher song_id, publisher_id Table song_artist song_id, artist_id Now I can't decide which is the better way. I'm not an expert on database design so If someone would point out the right direction. It would awesome. Are there any performance issues between two approaches? Thanks

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• Database design suggestions for a configurable product eshop

  - by solomongaby

  Hello, I am biulding an e-shop that will have configurable products. The configurable parts will need to have different prices and stocks from the main product. What database design would be best in this case? I started with something like this. Features id name Features Options id id_feature value Products id name price Products Features id id_product id_feature value ( save the value from the feature-options for ease in search ) configurable (yes, no) The problem is that now I am stuck on how to save the configurable product features. I was thinking of saving their value as a json. But that will make saving price modification for a certain option difficult. How would you go about this ? Thank you.

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• What open source database platform is most easily transferred from my personal machine into a window

  - by Tom

  I would like eventual interaction with MS Dynamics SL and/or MindTouch Core (running on WMware) for eventual intranet and/or internet display. I guess I am asking for front and back end recommendations for a database I am constructing, but since this is my first major project I would greatly appreciate any help and advice. I would also love an opportunity to learn a new language so the code base could be in any language. I do have a few more related questions for discussion; What is the viability of using Google hosting to provide the service to the public for free? Should I implement plone or another CMS if I have a large amount of output? Is there a structuring questionnaire or standards publication I could reference? Does UML diagramming provide additional options for portability? Thank you.

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• What is wrong with this database query?

  - by outsyncof

  I have the following tables in a database (i'll only list the important attributes): Person(ssn,countryofbirth) Parents(ssn,fatherbirthcountry) Employment(ssn, companyID) Company(companyID, name) My task is this: given fatherbirthcountry as input, output the names of companies where persons work whose countryofbirth match the fatherbirthcountry input. I pretend that the fatherbirthcountry is Mexico and do this: SELECT name FROM Company WHERE companyid = (SELECT companyid FROM Employment WHERE ssn = (SELECT ssn FROM Person WHERE countryofbirth = 'Mexico'); but it is giving me an error: >Scalar subquery is only allowed to return a single row. am I completely off track? Can anybody please help?

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• Is it OK to re-create many SQL connections (SQL 2008)

  - by Mr. Flibble

  When performing many inserts into a database I would usually have code like this: using (var connection = new SqlConnection(connStr)) { connection.Open(); foreach (var item in items) { var cmd = new SqlCommand("INSERT ...") cmd.ExecuteNonQuery(); } } I now want to shard the database and therefore need to choose the connection string based on the item being inserted. This would make my code run more like this foreach (var item in items) { connStr = GetConnectionString(item); using (var connection = new SqlConnection(connStr)) { connection.Open(); var cmd = new SqlCommand("INSERT ...") cmd.ExecuteNonQuery(); } } Which basically means it's creating a new connection to the database for each item. Will this work or will recreating connections for each insert cause terrible overhead?

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