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  • Check For Duplicate Records VS try/catch Unique Key Constraint

    - by Jed
    I have a database table that has a Unique Key constraint defined to avoid duplicate records from occurring. I'm curious if it is bad practice to NOT manually check for duplicate records prior to running an INSERT statement on the table. In other words, should I run a SELECT statement using a WHERE clause that checks for duplicate values of the record that I am about to INSERT. If a record is found, then do not run the INSERT statement, otherwise go ahead and run the INSERT.... OR Just run the INSERT statement and try/catch the exception that may be thrown due to a Unique Key violation. I'm weighing the two perspectives and can't decide which is best- 1. Don't waste a SELECT call to check for duplicates when I can just trap for an exception VS 2. Don't be lazy by implementing ugly try/catch logic VS 3. ???Your thoughts here??? :)

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  • How can I adjust the CommandTImeout in DbFit for long running queries?

    - by Ben Farmer
    Is there any way to increase the CommandTimeout for DbFit queries? I have a long running stored procedure that times out when running it in a DbFit Test. It's possible for the procedure to run for a really long time (processing millions of records) and would like to have DbFit wait until it's completed, even if it takes several minutes. We are using the latest version of FitSharp (downloaded it yesterday) and use the version of DbFit that is included with FitSharp.

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  • Historical / auditable database

    - by Mark
    Hi all, This question is related to the schema that can be found in one of my other questions here. Basically in my database I store users, locations, sensors amongst other things. All of these things are editable in the system by users, and deletable. However - when an item is edited or deleted I need to store the old data; I need to be able to see what the data was before the change. There are also non-editable items in the database, such as "readings". They are more of a log really. Readings are logged against sensors, because its the reading for a particular sensor. If I generate a report of readings, I need to be able to see what the attributes for a location or sensor was at the time of the reading. Basically I should be able to reconstruct the data for any point in time. Now, I've done this before and got it working well by adding the following columns to each editable table: valid_from valid_to edited_by If valid_to = 9999-12-31 23:59:59 then that's the current record. If valid_to equals valid_from, then the record is deleted. However, I was never happy with the triggers I needed to use to enforce foreign key consistency. I can possibly avoid triggers by using the extension to the "PostgreSQL" database. This provides a column type called "period" which allows you to store a period of time between two dates, and then allows you to do CHECK constraints to prevent overlapping periods. That might be an answer. I am wondering though if there is another way. I've seen people mention using special historical tables, but I don't really like the thought of maintainling 2 tables for almost every 1 table (though it still might be a possibility). Maybe I could cut down my initial implementation to not bother checking the consistency of records that aren't "current" - i.e. only bother to check constraints on records where the valid_to is 9999-12-31 23:59:59. Afterall, the people who use historical tables do not seem to have constraint checks on those tables (for the same reason, you'd need triggers). Does anyone have any thoughts about this? PS - the title also mentions auditable database. In the previous system I mentioned, there is always the edited_by field. This allowed all changes to be tracked so we could always see who changed a record. Not sure how much difference that might make. Thanks.

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  • Why index_merge is not used here?

    - by user198729
    Setup: mysql> create table t(a integer unsigned,b integer unsigned); mysql> insert into t(a,b) values (1,2),(1,3),(2,4); mysql> create index i_t_a on t(a); mysql> create index i_t_b on t(b); mysql> explain select * from t where a=1 or b=4; +----+-------------+-------+------+---------------+------+---------+------+------+-------------+ | id | select_type | table | type | possible_keys | key | key_len | ref | rows | Extra | +----+-------------+-------+------+---------------+------+---------+------+------+-------------+ | 1 | SIMPLE | t | ALL | i_t_a,i_t_b | NULL | NULL | NULL | 3 | Using where | +----+-------------+-------+------+---------------+------+---------+------+------+-------------+ Is there something I'm missing?

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  • javax.sql.DataSource.getConnection() locks system

    - by Ryan Elkins
    I'm using the Apache Commons DBCP library for connection pooling in a desktop application. I've done this before and never had a problem but the latest application has started sometimes locking up on the call to getConnection() on my DataSource. The application just hangs after that call. I'm closing up my resources when I'm done with them. Is there any known reason why this might happen? I'm not even sure where to being troubleshooting this now that I've got it narrowed down to this method. It doesn't always hang - sometimes it happens fairly quickly, sometimes it takes a long time. Sometimes it doesn't happen at all, although lately I can get it to happen within a few minutes.

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  • One table, need multiple values from different rows/tuples

    - by WmasterJ
    I have tables like: 'profile_values' userID | fid | value -------+---------+------- 1 | 3 | [email protected] 1 | 45 | 203-234-2345 3 | 3 | [email protected] 1 | 45 | 123-456-7890 And: 'users' userID | name -------+------- 1 | joe 2 | jane 3 | jake I want to join them and have one row with two of the values like: 'profile_values' userID | name | email | phone -------+-------+----------------+-------------- 1 | joe | [email protected] | 203-234-2345 2 | jane | [email protected] | 123-456-7890 I have solved it but it feels clumsy and I want to know if there is a better way to do it. Meaning solutions that are either more readable or faster(optimized) or simply best-practice. Current solution: multiple tables selected, many conditional statements: SELECT u.userID AS memberid, u.name AS first_name, pv1.value AS fname, pv2.value as lname FROM users AS u, profile_values AS pv1, profile_values AS pv2, WHERE u.userID = pv1.userID AND pv1.fid = 3 AND u.userID = pv2.userID AND pv2.fid = 45; Thanks for the help!

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  • How to get the last element by date of each "type" in LINQ or TSQL

    - by Mauro
    Imagine to have a table defined as CREATE TABLE [dbo].[Price]( [ID] [int] NOT NULL, [StartDate] [datetime] NOT NULL, [Price] [int] NOT NULL ) where ID is the identifier of an action having a certain Price. This price can be updated if necessary by adding a new line with the same ID, different Price, and a more recent date. So with a set of a data like ID StartDate Price 1 01/01/2009 10 1 01/01/2010 20 2 01/01/2009 10 2 01/01/2010 20 How to obtain a set like the following? 1 01/01/2010 20 2 01/01/2010 20

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  • Adding miliseconds to a datetime in tsql INSERT INTO

    - by DavRob60
    I'm doing a INSERT INTO query in order to initialize a new table. The primary key is RFQ_ID and Action_Time How could add 1 milisecond to each Action_Time on new record in order to avoid "Violation of PRIMARY KEY constraint" INSERT INTO QSW_RFQ_Log (RFQ_ID, Action_Time, Quote_ID) SELECT RFQ_ID , GETDATE() AS Action_Time , Quote_ID , 'Added to RFQ on Initialization' AS Note FROM QSW_Quote

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  • LINQ: Create persistable Associations in Code, Without Foreign Key

    - by Alex
    Hello, I know that I can create LINQ Associations without a Foreign Key. The problem is, I've been doing this by adding the [Association] attribute in the DBML file (same as through the designer), which will get erased again after I refresh my database (and reload the entire table structure). I know that there is the MyData.cs file (as part of the DBML) in which I can place my partial extensions etc. to domain objects (to persist even after I refresh the DBML), but I don't know how to create an association there?

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  • MySQL index building performance

    - by Christian
    I tried to build an index over a two columns of a 30,000,000 entry database. I canceled the process after ~60hr as it didn't seem to work. For some reason MySQL takes only 22 mb ram instead of using the RAM fully. Is index building an operation that needs no Ram or is there some way to tell MySQL to use more RAM to be faster?

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  • Nullable Integer ? (working with linq)

    - by nCdy
    I've got exception about convert NULL to Int32. I've got a table from database with nullable tinyint [Column(Storage="_StatType", DbType="tinyint NULL")] public StatType : int { get { _StatType; } } (to get C# code just replace variable's type) and after making linq select def StartLinq = linq <#from lpi in _CfgListParIzm where lpi.ID_ListParIzm==drr1 select (lpi.StatType) #> ; StartLinq.ToArray()[0] can't be readed if that is null :-/ mutable STT : int = 0; try { _=int.TryParse(StartLinq.ToArray()[0].ToString(), out STT); } catch { | _ is Exception => () /* I don't care*/ } upper code is very poor trick :( I wont use it.

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  • Self-referencing tables in Linq2Sql

    - by J-Man
    Hi, I've seen a lot of questions on self-referencing tables in Linq2Sql and how to eagerly load all child records for a particular root object. I've implemented a temporary solution by accessing all underlying properties, but you can see that this doesn't do the performance any good. The thing is though, that all records are correlated with each-other using a correlation GUID. Example below: RootElement - Id: 1 - ParentId: null - CorrelationId: 4D68E512-4B55-44f4-BA5A-174B630A03DD ChildElement1 - Id: 2 - ParentId: 1 - CorrelationId: 4D68E512-4B55-44f4-BA5A-174B630A03DD ChildElement2 - Id: 3 - ParentId: 2 - CorrelationId: 4D68E512-4B55-44f4-BA5A-174B630A03DD ChildElement1 - Id: 4 - ParentId: 2 - CorrelationId: 4D68E512-4B55-44f4-BA5A-174B630A03DD In my case, I do have access to the correlationId, so I can retrieve all of my records by performing the following query: from element in db.Elements where element.CorrelationId == '4D68E512-4B55-44f4-BA5A-174B630A03DD' select element; But, of course, I want these elements associated with each other by executing this query: from element in db.Elements where element.CorrelationId == '4D68E512-4B55-44f4-BA5A-174B630A03DD' && element.ParentId == null select element; My question is: is it possible to combine the results the first query as some sort of 'caching mechanism' for the query where I get the root element? Thanks for the input. J.

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  • PHP Error - Login Script

    - by gamerzfuse
    I am creating a new login script/members directory. I am creating it from scratch without any frameworks (advice on this matter would also be appreciated). The situation: // Look up the username and password in the database $query = "SELECT admin_id, username FROM admin WHERE adminname = '$admin_user' AND password = SHA1('$admin_pass')"; $data = mysqli_query($dbc, $query); if (mysqli_num_rows($data) == 1) { This bit of code keeps giving me an error (the last line in particular): Warning: mysqli_num_rows() expects parameter 1 to be mysqli_result, boolean given in /home8/craighoo/public_html/employees/security/dir_admin.php on line 20 When echoing the query I get: SELECT admin_id, username FROM admin WHERE adminname = 'admin' AND password = SHA1('tera#byte') Thanks in advance!

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  • MsSQL 2005 query performance

    - by Max
    I have the following query: select ............. from //one table and about 20 left joins// where ( ( this_.driverName like 'blah*' or this_.renterName like 'blah*' ) or exists ( select this0__.id as y0_ from ThirdParty this0__ where this0__.name like 'blah*' and this0__.claim_id=this_.id ) ) order by this_.id asc And I have two environment: One with 175 000 records in table "this_" and second with 25 000 records in table "this_". This query works right on 175k database and it works smth about 2 seconds, but on base with 25k this query freezes. and if drop one the folloing item from where clause: ( this_.driverName like 'blah*' or this_.renterName like 'blah*' ) or exists ( select this0__.id as y0_ from ThirdParty this0__ where this0__.name like 'blah*' and this0__.claim_id=this_.id ) query runs normally. How can I to increase performance of this query?

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  • MySQL optimized sentence

    - by Ivan
    I have a simple table where I have to extract some records. The problem is that the evaluation function is a very time-consuming stored procedure so I shouldn't to call it twice like in this sentence: SELECT *, slow_sp(row) FROM table WHERE slow_sp(row)>0 ORDER BY dist DESC LIMIT 10 First I thought in optimize like this: SELECT *, slow_sp(row) AS value FROM table WHERE value>0 ORDER BY dist DESC LIMIT 10 But it doesn't works due "value" is not processed when the WHERE clause is evaluated. Any idea to optimize this sentence? Thanks.

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  • How to add a column via a query which counts the total rows with a specific criteria in a table with circular relationship in MS ACCESS 2007

    - by Xaqron
    I have a simple table "Employees" with this fields: ID, ParentID, Name ParentID is Nullable since an employee may have no Manager. This table has a one-to-many relationship with itself: ID --one--to--many--> ParentID Now I want a query which returns this columns: Name, Count of rows where their ParentID equals to the current row ID (the row is the manager of that rows) Sample Table: ID | ParentID | Name ====================== 1 | 0 | John ---------------------- 2 | 1 | Bob ---------------------- 3 | 1 | Alice ---------------------- 4 | 3 | Jack This way I can find an employee is the manager of how many other employees. The result should be something like this: Name | Count of Employees ========================== John | 2 -------------- Bob | 0 -------------- Alice | 1 -------------- Jack | 0 How can I achieve this in MS ACCESS 2007? * I have tried built-in query builder without any success.

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  • Is my understanding of "select distinct" correct?

    - by paxdiablo
    We recently discovered a performance problem with one of our systems and I think I have the fix but I'm not certain my understanding is correct. In simplest form, we have a table blah into which we accumulate various values based on a key field. The basic form is: recdate date rectime time system varchar(20) count integer accum1 integer accum2 integer There are a lot more accumulators than that but they're all of the same form. The primary key is made up of recdate, rectime and system. As values are collected to the table, the count for a given recdate/rectime/system is incremented and the values for that key are added to the accumulators. That means the averages can be obtained by using accumN / count. Now we also have a view over that table specified as follows: create view blah_v ( recdate, rectime, system, count, accum1, accum2 ) as select distinct recdate, rectime, system, count, value (case when count > 0 then accum1 / count end, 0), value (case when count > 0 then accum2 / count end, 0) from blah; In other words, the view gives us the average value of the accumulators rather than the sums. It also makes sure we don't get a divide-by-zero in those cases where the count is zero (these records do exist and we are not allowed to remove them so don't bother telling me they're rubbish - you're preaching to the choir). We've noticed that the time difference between doing: select distinct recdate from XX varies greatly depending on whether we use the table or the view. I'm talking about the difference being 1 second for the table and 27 seconds for the view (with 100K rows). We actually tracked it back to the select distinct. What seems to be happening is that the DBMS is actually loading all the rows in and sorting them so as to remove duplicates. That's fair enough, it's what we stupidly told it to do. But I'm pretty sure the fact that the view includes every component of the primary key means that it's impossible to have duplicates anyway. We've validated the problem since, if we create another view without the distinct, it performs at the same speed as the underlying table. I just wanted to confirm my understanding that a select distinct can not have duplicates if it includes all the primary key components. If that's so, then we can simply change the view appropriately.

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  • Asynchronous callback - gwt

    - by sprasad12
    Hi, I am using gwt and postgres for my project. On the front end i have few widgets whose data i am trying to save on to tables at the back-end when i click on "save project" button(this also takes the name for the created project). In the asynchronous callback part i am setting more than one table. But it is not sending the data properly. I am getting the following error: org.postgresql.util.PSQLException: ERROR: insert or update on table "entitytype" violates foreign key constraint "entitytype_pname_fkey" Detail: Key (pname)=(Project Name) is not present in table "project". But when i do the select statement on project table i can see that the project name is present. Here is how the callback part looks like: oksave.addClickHandler(new ClickHandler(){ @Override public void onClick(ClickEvent event) { if(erasync == null) erasync = GWT.create(EntityRelationService.class); AsyncCallback<Void> callback = new AsyncCallback<Void>(){ @Override public void onFailure(Throwable caught) { } @Override public void onSuccess(Void result){ } }; erasync.setProjects(projectname, callback); for(int i = 0; i < boundaryPanel.getWidgetCount(); i++){ top = new Integer(boundaryPanel.getWidget(i).getAbsoluteTop()).toString(); left = new Integer(boundaryPanel.getWidget(i).getAbsoluteLeft()).toString(); if(widgetTitle.startsWith("ATTR")){ type = "regular"; erasync.setEntityAttribute(name1, name, type, top, left, projectname, callback); } else{ erasync.setEntityType(name, top, left, projectname, callback); } } } Question: Is it wrong to set more than one in the asynchronous callback where all the other tables are dependent on a particular table? when i say setProjects in the above code isn't it first completed and then moved on to the next one? Please any input will be greatly appreciated. Thank you.

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  • ALTER TABLE on dependant column

    - by Sharmi
    I am trying to alter column datatype of a primary key to tinyint from int.This column is a foreign key in other tables.So,I get the following error: Msg 5074, Level 16, State 1, Line 1 The object 'PK_User_tbl' is dependent on column 'appId'. Msg 5074, Level 16, State 1, Line 1 The object 'FK_Details_tbl_User_tbl' is dependent on column 'appId'. Msg 5074, Level 16, State 1, Line 1 The object 'FK_Log_tbl_User_tbl' is dependent on column 'appId'. Msg 4922, Level 16, State 9, Line 1 ALTER TABLE ALTER COLUMN appId failed because one or more objects access this column. Howw should i rectify this?

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  • Testing the context in asp.net mvc

    - by user252160
    I got pretty experienced with testing controllers, my question here is though, aren't we supposed to test the data context as well, and how ? I mean, there are a lot of relationships and constraints coming from the DB that simply testing controllers does not cover. On the other hand, testing against the DB is not considered a good practice - what then ? Simply testing without db.SubmitChanges() or what ?

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  • Count times ID appears in a table and return in row.

    - by Tyler
    SELECT Boats.id, Boats.date, Boats.section, Boats.raft, river_company.company, river_section.section AS river FROM Boats INNER JOIN river_company ON Boats.raft = river_company.id INNER JOIN river_section ON Boats.section = river_section.id ORDER BY Boats.date DESC, river, river_company.company Returns everything I need. But how would I add a [Photos] table and count how many times Boats.id occurs in it and add that to the returned rows. So if there are 5 photos for boat #17 I want the record for boat #17 to say PhotoCount = 5

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  • Applying Domain Model on top of Linq2Sql entities

    - by Thomas
    I am trying to practice the model first approach and I am putting together a domain model. My requirement is pretty simple: UserSession can have multiple ShoppingCartItems. I should start off by saying that I am going to apply the domain model interfaces to Linq2Sql generated entities (using partial classes). My requirement translates into three database tables (UserSession, Product, ShoppingCartItem where ProductId and UserSessionId are foreign keys in the ShoppingCartItem table). Linq2Sql generates these entities for me. I know I shouldn't even be dealing with the database at this point but I think it is important to mention. The aggregate root is UserSession as a ShoppingCartItem can not exist without a UserSession but I am unclear on the rest. What about Product? It is defiently an entity but should it be associated to ShoppingCartItem? Here are a few suggestion (they might all be incorrect implementations): public interface IUserSession { public Guid Id { get; set; } public IList<IShoppingCartItem> ShoppingCartItems{ get; set; } } public interface IShoppingCartItem { public Guid UserSessionId { get; set; } public int ProductId { get; set; } } Another one would be: public interface IUserSession { public Guid Id { get; set; } public IList<IShoppingCartItem> ShoppingCartItems{ get; set; } } public interface IShoppingCartItem { public Guid UserSessionId { get; set; } public IProduct Product { get; set; } } A third one is: public interface IUserSession { public Guid Id { get; set; } public IList<IShoppingCartItemColletion> ShoppingCartItems{ get; set; } } public interface IShoppingCartItemColletion { public IUserSession UserSession { get; set; } public IProduct Product { get; set; } } public interface IProduct { public int ProductId { get; set; } } I have a feeling my mind is too tightly coupled with database models and tables which is making this hard to grasp. Anyone care to decouple?

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  • Table Partitioning

    - by Ankur Gahlot
    How advantageous is it to use partitioning of tables as compared to normal approach ? Is there a sort of sample case or detailed comparative analysis that could statistically ( i know this is too strong a word, but it would really help if it is illustrated by some numbers ) emphasize on the utility of the process. Thanks, Ankur

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