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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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  • check if sqlserver is installed on a machine thro C#

    - by Skun
    Hey ! I am making an application which is a user interface to access 2 types of databases - SQLite and MSSQL server. The thing is, SQLite doesnt need to be "installed" since its just a flatfile database, but on the other hand, SQLserver (Express/normal) need to be installed before use. My Question is simple: Is there a way by which i can find out if an instance of SQLserver has been installed on the local machine by using a C# program?

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  • How to completely remove MySQL from a windows 7 machine

    - by Jazibobs
    I'm new to MySQL struggling to find a version and workbench which works stably on my 64 bit windows 7 machine. I've decided to attempt to completely remove MySQL from my machine and to restart the installation process from scratch. However, after uninstalling all software linked with MySQL using conventional control panel uninstalling means some MySQL windows services still remain on my machine. I can't see any obvious method to remove these and they have since been causing me difficulties when trying to install different versions of MySQL. Could anyone please advise?

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  • Best practice for avoiding locks on a heavily read table?

    - by Luiggi
    Hi, I have a big database (~4GB), with 2 large tables (~3M records) having ~180K SELECTs/hour, ~2k UPDATEs/hour and ~1k INSERTs+DELETEs/hour. What would be the best practice to guarantee no locks for the reading tasks while inserting/updating/deleting? I was thinking about using a NOLOCK hint, but there is so much discussed about this (is good, is bad, it depends) that I'm a bit lost. I must say I've tried this in a dev environment and I didn't find any problems, but I don't want to put it on production until I get some feedback... Thank you! Luiggi

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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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  • sports league database design

    - by John
    Hello, I'm developing a database to store statistics for a sports league. I'd like to show several tables: - league table that indicates the position of the team in the current and previous fixture - table that shows the position of a team in every fixture in the championship I have a matches table: Matches (IdMatch, IdTeam1, IdTeam2, GoalsTeam1, GoalsTeam2) Whith this table I can calculate the total points of every team based on the matches the team played. But every time I want to show the league table I have to calculate the points. Also I have a problem to calculate in which position classified a team in the last 10 fixtures cause I have to make 10 queries. To store the league table for every fixture in a database table is another approach, but every time I change a match already played I have to recalculate every fixture from there... Is there a better approach for this problem? Thanks

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  • Create an index only on certain rows in mysql

    - by dhruvbird
    So, I have this funny requirement of creating an index on a table only on a certain set of rows. This is what my table looks like: USER: userid, friendid, created, blah0, blah1, ..., blahN Now, I'd like to create an index on: (userid, friendid, created) but only on those rows where userid = friendid. The reason being that this index is only going to be used to satisfy queries where the WHERE clause contains "userid = friendid". There will be many rows where this is NOT the case, and I really don't want to waste all that extra space on the index. Another option would be to create a table (query table) which is populated on insert/update of this table and create a trigger to do so, but again I am guessing an index on that table would mean that the data would be stored twice. How does mysql store Primary Keys? I mean is the table ordered on the Primary Key or is it ordered by insert order and the PK is like a normal unique index? I checked up on clustered indexes (http://dev.mysql.com/doc/refman/5.0/en/innodb-index-types.html), but it seems only InnoDB supports them. I am using MyISAM (I mention this because then I could have created a clustered index on these 3 fields in the query table). I am basically looking for something like this: ALTER TABLE USERS ADD INDEX (userid, friendid, created) WHERE userid=friendid

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  • excel quotes in formula question

    - by I__
    i have a column with this data: IT_AMPH IT_BARB IT_BENZ IT_BUP SOMA i want the column next to it to be literarely =like "*,IT_AMPH,*" =like "*,IT_BARB,*" =like "*,IT_BENZ,*" etc please note that i want the equal signed to be displayed, exactly as shown above what would be the formula for this?

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  • Merging some columns of two mysql tables where id = fileid

    - by garg
    There are two tables TableA filedata_id | user_id | filename 1 | 1 | file.txt 2 | 1 | file2.txt TableB a_id | date | filedataid | counter | state | cat_id | subcat_id | med_id 99 | 1242144 | 1 | 2 | v | 55 | 56 | 90 100 | 1231232 | 2 | 3 | i | 44 | 55 | 110 I want to move columns cat_id, subcat_id, med_id to TableA where tableA.filedata_id = TableB.filedataid The result should be: TableA filedata_id | user_id | filename | cat_id | subcat_id | med_id 1 | 1 | file.txt | 55 | 56 | 90 2 | 1 | file2.txt | 44 | 55 | 110 and so on. Is there a way to do this easily?

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  • Linqbuilder Query with an OrderBy

    - by Renshai
    I have a 1 : M relationship. I built a dynamic query based on input from users to return the listing of parents entities along with their children (using predicate builder: (done successfully new TDataContext().Ps.Where(predicate) )... but need to order the results by a field found only on the child entities. I'm at a loss: new TDataContext().Ps.Where(predicate).OrderBy(p = p.Cs. ??) where Ps = parents collection relationship with Cs = child entities any help appreciated.

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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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  • How to structure data... Sequential or Hierarchical?

    - by Ryan
    I'm going through the exercise of building a CMS that will organize a lot of the common documents that my employer generates each time we get a new sales order. Each new sales order gets a 5 digit number (12222,12223,122224, etc...) but internally we have applied a hierarchy to these numbers: + 121XX |--01 |--02 + 122XX |--22 |--23 |--24 In my table for sales orders, is it better to use the 5 digital number as an ID and populate up or would it be better to use the hierarchical structure that we use when referring to jobs in regular conversation? The only benefit to not populating sequentially seems to be formatting the data later on in my view, but that doesn't sound like a good enough reason to go through the extra work. Thanks

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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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  • Group mysql query by 15 min intervals

    - by gsiener
    I've got a monitoring system that is collecting data every n seconds (n ~=10 but varies). I'd like to aggregate the collected data by 15 minute intervals. Is there a way to corral the timestamp column into 15 minute chunks to allow for grouping to work?

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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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  • How to create festival calendar in ASP.net

    - by Atul
    I want to make a festival calendar using asp.net from that I used two ajax calendar and one textbox it is a festival textbox where we enter festival which FromDate and ToDate respectively. I want to do this as following point If I enter in textbox Christmas and Choose Fromdate=25/12/2011 and ToDate=31/12/2011 then it will be valid If I choose fromDate=25/12/2011 and ToDate=24/12/2011 then it will invalid If I choose Fromdate=25/12/2011 and Todate=28/12/2011 then also it is invalid because it coming in between 25/12/2011 and 31/12/2011 If I Choose fromdate=1/1/2011 and ToDate=1/1/2011 then it is valid If I choose fromdate=21/12/2011 and 25/12/2011 then it is invalid because of already Christmas done in 1/1/2011 And all date should show in gridview like 25-dec-2011 format Here is my code: DateTime dt1 = Convert.ToDateTime(txt_fromdate.Text); DateTime dt2 = Convert.ToDateTime(txt_todate.Text); if (dt1 > dt2) { con.Open(); com = new SqlCommand("BTNN_MovieDB_Festival_Details_Insert", con); com.Parameters.Add("@fromdate", SqlDbType.VarChar).Value = dateformat_mmdd(txt_fromdate.Text.ToString().Trim()); com.Parameters.Add("@todate", SqlDbType.VarChar).Value = dateformat_mmdd(txt_todate.Text.ToString().Trim()); com.Parameters.Add("@return", SqlDbType.VarChar).Direction = ParameterDirection.ReturnValue; com.ExecuteNonQuery(); con.Close(); showdata(); } else if (dt1 < dt2) { lblerror.Text = "ToDate should be greater than FromDate"; }

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  • SQL Server - How Do I Substract 2 Hours from Formatted Time

    - by user1842653
    I need to know how to add 2 hours to the below 'Completed' timestamp. Here is the Select statement Select Tsk.task_id,Tsk.org_id,Tsk.completed,Tsk.assgn_acct_id,name FROM tdstelecom.tasks As Tsk WHERE Tsk.task_id = '11094836' AND DATE(Tsk.completed) < CURDATE() AND DATE(Tsk.completed) >= DATE_SUB(CURDATE (),INTERVAL 180 DAY) Here are the results: 2012-08-22 14:18:14 Desired results: 2012-08-22 16:18:14

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