BorlandTalk.com Borland discussion newsgroups   Archives   FAQ   Search   Memberlist   Usergroups   Register   Profile   Log in to check your private messages   Log in  NULL Concatenation Behavior          BorlandTalk.com Forum Index -> Delphi Databases (SQL Servers) View previous topic :: View next topic   Author Message Penny Guest Posted: Fri Oct 01, 2004 10:01 am    Post subject: NULL Concatenation Behavior Hi, I want to concatenate to strings, but both can be null. e.g. 'AAA' + 'aaa' = 'AAAaaa' 'BBB' + null = 'BBB' When I' m doing this I have e.g. 'AAA' + 'aaa' = 'AAAaaa' 'BBB' + null = null I found that this have to do with DBPROPVAL_CB_NULL, DBPROPVAL_CB_NON_NULL but I can find how to change it. Any ideas? Thanks Back to top Martijn Tonies Guest Posted: Fri Oct 01, 2004 10:08 am    Post subject: Re: NULL Concatenation Behavior Hello, Quote: I want to concatenate to strings, but both can be null. e.g. 'AAA' + 'aaa' = 'AAAaaa' 'BBB' + null = 'BBB' When I' m doing this I have e.g. 'AAA' + 'aaa' = 'AAAaaa' 'BBB' + null = null I found that this have to do with DBPROPVAL_CB_NULL, DBPROPVAL_CB_NON_NULL but I can find how to change it. Are you using MS SQL? If so, take a look at: SET CONCAT_NULL_YIELDS_NULL { ON | OFF } To change the behaviour, or, better yet: COALESCE to change the NULL to an empty string: 'AAA' + COALESCE(someotherthing, '') -- With regards, Martijn Tonies Database Workbench - developer tool for InterBase, Firebird, MySQL & MS SQL Server. Upscene Productions http://www.upscene.com Back to top Penny Guest Posted: Fri Oct 01, 2004 1:00 pm    Post subject: Re: NULL Concatenation Behavior I use SQL Server 2000 I tried those : use master exec sp_dboption 'TestDB','concat null yields null','False' and also ALTER DATABASE StoresEmpty SET CONCAT_NULL_YIELDS_NULL OFF but it continues to result in Null. COALESCE works but I don't want to change all my queries. Moreover, I read from the help that default value of "concat null yields null" is False, so why that happens to me, that I surely never changed it. Thanks. "Martijn Tonies" <m.tonies@upscene!nospam!.com> wrote Quote: Hello, I want to concatenate to strings, but both can be null. e.g. 'AAA' + 'aaa' = 'AAAaaa' 'BBB' + null = 'BBB' When I' m doing this I have e.g. 'AAA' + 'aaa' = 'AAAaaa' 'BBB' + null = null I found that this have to do with DBPROPVAL_CB_NULL, DBPROPVAL_CB_NON_NULL but I can find how to change it. Are you using MS SQL? If so, take a look at: SET CONCAT_NULL_YIELDS_NULL { ON | OFF } To change the behaviour, or, better yet: COALESCE to change the NULL to an empty string: 'AAA' + COALESCE(someotherthing, '') -- With regards, Martijn Tonies Database Workbench - developer tool for InterBase, Firebird, MySQL & MS SQL Server. Upscene Productions http://www.upscene.com Back to top Martijn Tonies Guest Posted: Fri Oct 01, 2004 1:39 pm    Post subject: Re: NULL Concatenation Behavior Quote: I use SQL Server 2000 I tried those : use master exec sp_dboption 'TestDB','concat null yields null','False' and also ALTER DATABASE StoresEmpty SET CONCAT_NULL_YIELDS_NULL OFF Have another look at the Help. There's info on how to set this on a per-database level and on a per-session level. -- With regards, Martijn Tonies Database Workbench - developer tool for InterBase, Firebird, MySQL & MS SQL Server. Upscene Productions http://www.upscene.com Back to top Pravin Taneja Guest Posted: Fri Oct 01, 2004 2:27 pm    Post subject: Re: NULL Concatenation Behavior Quote: COALESCE works but I don't want to change all my queries. You can create a view that uses COALESCE (to return '' for null fields) and from your queries you use the view instead of the table name. This way you wont have to change your program if you need to switch to another RDBMS but you will have to write similar views using the syntax of target RDBMS to achieve the same thing. 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