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  • What is the difference between check and foreign key?

    - by GigaPr
    Hi, i am quite confused about the difference between a FOREIGN KEY and CHECK constraint. they appear to me to achieve the same result. I mean I could create a table and enforce a Foreign key on another table, but i could create a CHECK to ensure the value in in another table. What is the difference and when to use the one or the other? thanks

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  • Updating counters through Hibernate

    - by at
    This is an extremely common situation, so I'm expecting a good solution. Basically we need to update counters in our tables. As an example a web page visit: Web_Page -------- Id Url Visit_Count So in hibernate, we might have this code: webPage.setVisitCount(webPage.getVisitCount()+1); The problem there is reads in mysql by default don't pay attention to transactions. So a highly trafficked webpage will have inaccurate counts. The way I'm used to doing this type of thing is simply call: update Web_Page set Visit_Count=Visit_Count+1 where Id=12345; I guess my question is, how do I do that in Hibernate? And secondly, how can I do an update like this in Hibernate which is a bit more complex? update Web_Page wp set wp.Visit_Count=(select stats.Visits from Statistics stats where stats.Web_Page_Id=wp.Id) + 1 where Id=12345;

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  • LinqtoSql Pre-compile Query problem with Count() on a group by

    - by Joe Pitz
    Have a LinqtoSql query that I now want to precompile. var unorderedc = from insp in sq.Inspections where insp.TestTimeStamp > dStartTime && insp.TestTimeStamp < dEndTime && insp.Model == "EP" && insp.TestResults != "P" group insp by new { insp.TestResults, insp.FailStep } into grp select new { FailedCount = (grp.Key.TestResults == "F" ? grp.Count() : 0), CancelCount = (grp.Key.TestResults == "C" ? grp.Count() : 0), grp.Key.TestResults, grp.Key.FailStep, PercentFailed = Convert.ToDecimal(1.0 * grp.Count() / tcount * 100) }; I have created this delegate: public static readonly Funct<SQLDataDataContext, int, string, string, DateTime, DateTime, IQueryable<CalcFailedTestResult>> GetInspData = CompiledQuery.Compile((SQLDataDataContext sq, int tcount, string strModel, string strTest, DateTime dStartTime, DateTime dEndTime, IQueryable<CalcFailedTestResult> CalcFailed) => from insp in sq.Inspections where insp.TestTimeStamp > dStartTime && insp.TestTimeStamp < dEndTime && insp.Model == strModel && insp.TestResults != strTest group insp by new { insp.TestResults, insp.FailStep } into grp select new { FailedCount = (grp.Key.TestResults == "F" ? grp.Count() : 0), CancelCount = (grp.Key.TestResults == "C" ? grp.Count() : 0), grp.Key.TestResults, grp.Key.FailStep, PercentFailed = Convert.ToDecimal(1.0 * grp.Count() / tcount * 100) }); The syntax error is on the CompileQuery.Compile() statement It appears to be related to the use of the select new {} syntax. In other pre-compiled queries I have written I have had to just use the select projection by it self. In this case I need to perform the grp.count() and the immediate if logic. I have searched SO and other references but cannot find the answer.

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  • Coalesce and Case-When with To_Date not working as expected (Postgres bug?)

    - by ADTC
    I'm using Postgres 9.1. The following query does not work as expected. Coalesce should return the first non-null value. However, this query returns null (1?) instead of the date (2). select COALESCE( TO_DATE('','yyyymmdd'), --(1) TO_DATE('20130201','yyyymmdd') --(2) ); --(1) this evaluates independently to null --(2) this evaluates independently to the date, and therefore is the first non-null value What am I doing wrong? Any workaround? Edit: This may have nothing to do with Coalesce at all. I tried some experiments with Case When constructs; it turns out, Postgres has this big ugly bug where it treats TO_DATE('','yyyymmdd') as not null, even though selecting it returns null.

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  • SSRS Performance Mystery

    - by user101654
    I have a stored procedure that returns about 50000 records in 10sec using at most 2 cores in SSMS. The SSRS report using the stored procedure was taking 20min and would max out the processor on an 8 core server for the entire time. The report was relatively simple (i.e. no graphs, calculations). The report did not appear to be the issue as I wrote the 50K rows to a temp table and the report could display the data in a few seconds. I tried many different ideas for testing altering the stored procedure each time, but keeping the original code in a separate window to revert back to. After one Alter of the stored procedure, going back to the original code, the report and server utilization started running fast, comparable to the performance of the stored procedure alone. Everything is fine for now, but I am would like to get to the bottom of what caused this in case it happens again. Any ideas?

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  • “Function” calling inside store procedure

    - by idimba
    Hi, I have a big store procedure, that contains a lot of INSERTs. There're many INSERTS that almost identical - they're different by some parameter(s) (all INSERTs to the same table) Is there a way to create a function/method, to which I'll pass the above parameter(s) and the function/method will generate concrete INSERT's? Thanks

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  • Merging rows with uniqueness constraints

    - by Flambino
    I've got a little time-tracking web app (implemented in Rails 3.2.8 & MySQL). The app has several users who add their time to specific tasks, on a given date. The system is set up so a user can only have 1 time entry (i.e. row) per task per date. I.e. if you add time twice on the same task and date, it'll add time to the existing row, rather than create a new one. Now I'm looking to merge 2 tasks. In the simplest terms, merging task ID 2 into task ID 1 would take this time | user_id | task_id | date ------+----------+----------+----------- 10 | 1 | 1 | 2012-10-29 15 | 2 | 1 | 2012-10-29 10 | 1 | 2 | 2012-10-29 5 | 3 | 2 | 2012-10-29 and change it into this time | user_id | task_id | date ------+----------+----------+----------- 20 | 1 | 1 | 2012-10-29 <-- time values merged (summed) 15 | 2 | 1 | 2012-10-29 <-- no change 5 | 3 | 1 | 2012-10-29 <-- task_id changed (no merging necessary) I.e. merge by summing the time values, where the given user_id/date/task combo would conflict. I figure I can use a unique constraint to do a ON DUPLICATE KEY UPDATE ... if I do an insert for every task_id=2 entry. But that seems pretty inelegant. I've also tried to figure a way to first update all the rows in task 1 with the summed-up times, but I can't quite figure that one out. Any ideas?

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  • How do I specify a default value in a MS Access query?

    - by jheddings
    I have three tables similar to the following: tblInvoices: Number | Date | Customer tblInvDetails: Invoice | Quantity | Rate | Description tblPayments: Invoice | Date | Amount I have created a query called exInvDetails that adds an Amount column to tblInvDetails: SELECT tblInvDetails.*, [tblInvDetails.Quantity]*[tblInvDetails.Rate]* AS Amount FROM tblInvDetails; I then created a query exInvoices to add Total and Balance columns to tblInvoices: SELECT tblInvoices.*, (SELECT Sum(exInvDetails.Amount) FROM exInvDetails WHERE exInvDetails.Invoice = tblInvoices.Number) AS Total, (SELECT Sum(tblPayments.Amount) FROM tblPayments WHERE tblPayments.Invoice = tblInvoices.Number) AS Payments, (Total-Payments) AS Balance FROM tblInvoices; If there are no corresponding payments in tblPayments, the fields are null instead of 0. Is there a way to force the resulting query to put a 0 in this column?

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  • Check for duplicate rows in 2 columns before update

    - by user3891378
    I have a table with 4 columns, and I need to check to see if a Column Pair exists before inserting a row into the database: INSERT INTO dbo.tblCallReport_Detail (fkCallReport, fkProductCategory, Discussion, Action) VALUES (?, ?, ?, ?) The pair in question is fkCallReport and fkProductCategory. For example if the row trying to be inserted has fkCallReport = 3 and fkProductCategory = 5, and the database already has both of those values together, it should display an error and ask if they would like to combine the Disuccsion and Action with the current record. Keep in mind I'm doing this in VBA Access 2010 and am still very new.

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  • I can't able to edit my column name after saving

    - by Midhun M
    I create a new table of employee now I want to edit one of the column name in that table. I can edit but while saving a pop up window asks to save some text file. How may I resolve this? Is it possible to edit without creating a new table? The text file is /* Friday, August 22, 20144:32:53 PM User: Server: MIDHUN\SQLEXPRESS Database: LinQ Application: */ employee

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  • What is the maximum length of a string parameter to Stored procedure?

    - by padmavathi
    I have a string of length 1,44,000 which has to be passed as a parameter to a stored procedure which is a select query on a table. When a give this is in a query (in c# ) its working fine. But when i pass it as a parameter to stored procedure its not working. Here is my stored procedure where in i have declared this parameter as NVARCHAR(MAX) ------------------------------------------------------ set ANSI_NULLS ON set QUOTED_IDENTIFIER ON go CREATE PROCEDURE [dbo].[ReadItemData](@ItemNames NVARCHAR(MAX),@TimeStamp as DATETIME) AS select * from ItemData where ItemName in (@ItemNames) AND TimeStamp=@TimeStamp --------------------------------------------------------------------- Here the parameter @ItemNames is a string concatinated with different names such as 'Item1','Item2','Item3'....etc. Can anyone tell what went wrong here? Thanks & Regards Padma

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  • MYSQL to UPDATE table if row with 2 specific columns exist or INSERT new row if it does not exist

    - by user2509541
    I have a MYSQL table that looks as follows: id id_jugador id_partido team1 team2 1 2 1 5 2 2 2 2 1 1 3 1 2 0 0 I need to create a query to either INSERT new rows in the table or UPDATE the table. The condition is based on id_jugador and id_partido, meaning that if I wanted to insert id_jugador = 2 and id_partido = 1, then it should just UPDATE the existing row with the new team1 and team2 values I am sending. And dont duplicate the row. However, if I have an entry id_jugador=2 and id_partido=3, since this combination does not exist yet, it should add the new row. I read about the REPLACE INTO but it seems to be unable to check combination of UNIQUE KEYS.

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  • LINQ - 'Could not translate expression' with previously used and proven query condition

    - by tomfumb
    I am fairly new to LINQ and can't get my head around some inconsistency in behaviour. Any knowledgeable input would be much appreciated. I see similar issues on SO and elsewhere but they don't seem to help. I have a very simple setup - a company table and an addresses table. Each company can have 0 or more addresses, and if 0 one must be specified as the main address. I'm trying to handle the cases where there are 0 addresses, using an outer join and altering the select statement accordingly. Please note I'm currently binding the output straight to a GridView so I would like to keep all processing within the query. The following DOES work IQueryable query = from comp in context.Companies join addr in context.Addresses on comp.CompanyID equals addr.CompanyID into outer // outer join companies to addresses table to include companies with no address from addr in outer.DefaultIfEmpty() where (addr.IsMain == null ? true : addr.IsMain) == true // if a company has no address ensure it is not ruled out by the IsMain condition - default to true if null select new { comp.CompanyID, comp.Name, AddressID = (addr.AddressID == null ? -1 : addr.AddressID), // use -1 to represent a company that has no addresses MainAddress = String.Format("{0}, {1}, {2} {3} ({4})", addr.Address1, addr.City, addr.Region, addr.PostalCode, addr.Country) }; but this displays an empty address in the GridView as ", , ()" So I updated the MainAddress field to be MainAddress = (addr.AddressID == null ? "" : String.Format("{0}, {1}, {2} {3} ({4})", addr.Address1, addr.City, addr.Region, addr.PostalCode, addr.Country)) and now I'm getting the Could not translate expression error and a bunch of spewey auto-generated code in the error which means very little to me. The condition I added to MainAddress is no different to the working condition on AddressID, so can anybody tell me what's going on here? Any help greatly appreciated.

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  • Database table schema design - varchar(n). Suitable choice of N

    - by morpheous
    Coming from a C background, I may be getting too anal about this and worrying unnecessarily about bits and bytes here. Still, I cant help thinking how the data is actually stored and that if I choose an N which is easily factorizable into a power of 2, the database will be more effecient in how it packs data etc. Using this "logic", I have a string field in a table which is a variable length up to 21 chars. I am tempted to use 32 instead of 21, for the reason given above - however now I am thinking that I am wasting disk space because there will be space allocated for 11 extra chars that are guaranteed to be never used. Since I envisage storing several tens of thousands of rows a day, it all adds up. Question: Mindful of all of the above, Should I declare varchar(21) or varchar(32) and why?

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  • Database design

    - by Hadad
    Hello, I've a system, that have two types of users (Companies and individuals).all types have a shared set of properties but they differ in another. What is the best design merge all in one table that allows null for unmatched properties, or separate them in two tables related to a basic table with a one to one relationship. Thanks.

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  • SQLite: Simple DELETE statement did not work

    - by user186446
    I have a table MRU, that has 3 columns. (VALUE varchar(255); TYPE varchar(20); DT_ADD datetime) This is a table simply storing an entry and recording the date time it was recorded. What I wanted to do is: delete the oldest entry whenever I add a new entry that exceeds a certain number. here is my query: delete from MRU where type = 'FILENAME' ORDER BY DT_ADD limit 1; The query returns an error. Thanks

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  • Mysql query problem

    - by Lost_in_code
    Below is a sample table: fruits +-------+---------+ | id | type | +-------+---------+ | 1 | apple | | 2 | orange | | 3 | banana | | 4 | apple | | 5 | apple | | 6 | apple | | 7 | orange | | 8 | apple | | 9 | apple | | 10 | banana | +-------+---------+ Following are the two queries of interest: SELECT * FROM fruits WHERE type='apple' LIMIT 2; SELECT COUNT(*) AS total FROM fruits WHERE type='apple'; // output 6 I want to combine these two queries so that the results looks like this: +-------+---------+---------+ | id | type | total | +-------+---------+---------+ | 1 | apple | 6 | | 4 | apple | 6 | +-------+---------+---------+ The output has to be limited to 2 records but it should also contain the total number of records of the type apple. How can this be done with 1 query?

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  • what is the 'extra' mean in this django code..

    - by zjm1126
    TOPIC_COUNT_SQL = """ SELECT COUNT(*) FROM topics_topic WHERE topics_topic.object_id = maps_map.id AND topics_topic.content_type_id = %s """ MEMBER_COUNT_SQL = """ SELECT COUNT(*) FROM maps_map_members WHERE maps_map_members.map_id = maps_map.id """ maps = maps.extra(select=SortedDict([ ('member_count', MEMBER_COUNT_SQL), ('topic_count', TOPIC_COUNT_SQL), ]), select_params=(content_type.id,)) i don't know this mean, thanks

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  • Sorting nested set by name while keep depth integrity

    - by wb
    I'm using the nested set model that'll later be used to build a sitemap for my web site. This is my table structure. create table departments ( id int identity(0, 1) primary key , lft int , rgt int , name nvarchar(60) ); insert into departments (lft, rgt, name) values (1, 10, 'departments'); insert into departments (lft, rgt, name) values (2, 3, 'd'); insert into departments (lft, rgt, name) values (4, 9, 'a'); insert into departments (lft, rgt, name) values (5, 6, 'b'); insert into departments (lft, rgt, name) values (7, 8, 'c'); How can I sort by depth as well as name? I can do select replicate('----', count(parent.name) - 1) + ' ' + node.name , count(parent.name) - 1 as depth , node.lft from departments node , departments parent where node.lft between parent.lft and parent.rgt group by node.name, node.lft order by depth asc, node.name asc; However, that does not match children with their parent for some reason. department lft rgt --------------------------- departments 0 1 ---- a 1 4 ---- d 1 2 -------- b 2 5 -------- c 2 7 As you can see, department 'd' has department 'a's children! Thank you.

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