InstantForum.NET v2.9.0SQLServerCentralhttp://www.sqlservercentral.com/Forums/notifications@sqlservercentral.comThu, 23 May 2013 23:59:17 GMT20http://www.sqlservercentral.com/Forums/Topic783416-8-1.aspx[quote][b]Marcin Gol [SQL Server MVP] (9/7/2009)[/b][hr]maybe other question is right here ... does the implemantion of checksum function has changed over the time ? (sql 2000 -> 2008?); if don't why im getting other values of checksum than Zahran ?[/quote]I get the same return values on SQL Server 2008.Tue, 08 Sep 2009 02:58:26 GMTFlorian Reischlhttp://www.sqlservercentral.com/Forums/Topic783416-8-1.aspx[quote][b]Marcin Gol [SQL Server MVP] (9/7/2009)[/b][hr][quote][b]Sergiy (9/7/2009)[/b][hr][quote][b]Marcin Gol [SQL Server MVP] (9/7/2009)[/b][hr]Sergiy - the paragraph you mentioned change nothing. hash is a hash - and for a given string should always return the same value. did you try to run his query on your sql ?[/quote]You probably did not reach the last sentence of the paragraph.;-)[/quote]i read it but i feel that we don't understand each other ;-)my version: for a given string we should always receive same hash, did i say that hash is unique? nope.maybe other question is right here ... does the implemantion of checksum function has changed over the time ? (sql 2000 -> 2008?); if don't why im getting other values of checksum than Zahran ?[/quote]It actually returns the same hash value for unchanged original value.Is it any different on you machine?And the topic was actually about uniqueness problem. My reference was about it.Mon, 07 Sep 2009 16:19:02 GMTSergiyhttp://www.sqlservercentral.com/Forums/Topic783416-8-1.aspx[quote][b]Sergiy (9/7/2009)[/b][hr][quote][b]Marcin Gol [SQL Server MVP] (9/7/2009)[/b][hr]Sergiy - the paragraph you mentioned change nothing. hash is a hash - and for a given string should always return the same value. did you try to run his query on your sql ?[/quote]You probably did not reach the last sentence of the paragraph.;-)[/quote]i read it but i feel that we don't understand each other ;-)my version: for a given string we should always receive same hash, did i say that hash is unique? nope.maybe other question is right here ... does the implemantion of checksum function has changed over the time ? (sql 2000 -> 2008?); if don't why im getting other values of checksum than Zahran ?Mon, 07 Sep 2009 16:09:22 GMTMarcin Golhttp://www.sqlservercentral.com/Forums/Topic783416-8-1.aspxHi ZahranLittle quote from BOL[quote]When an MD5 hash algorithm is specified, the probability of HashBytes returning the same result for two different inputs is much lower than that of CHECKSUM.[/quote]Keep in mind. A hash is as unique as possible, but it's not a guarantee for [b]real[/b] uniqueness. If you have a VARCHAR(100) column it represents much more possible values than an INT.You can use HASHBYTES or BINARY_CHECKSUM to get a better hash than old CHECKSUM function.[code]SELECT HASHBYTES('MD5', CustomerNo + Address) ,BINARY_CHECKSUM(CustomerNo, Address) ,CHECKSUM(CustomerNo, Address)FROM @checksum[/code]Anyway, a hash will never be a 100% guarantee for uniqueness. If you need unique values use an IDENTITY column or a GUID.GreetsFlo[i]Edit: Dang! Sorry, didn't notice this is the 2000 forum. Probably the new functions are not available...[/i]Mon, 07 Sep 2009 15:37:30 GMTFlorian Reischlhttp://www.sqlservercentral.com/Forums/Topic783416-8-1.aspx[quote][b]Marcin Gol [SQL Server MVP] (9/7/2009)[/b][hr]Sergiy - the paragrah you mentioned change nothing. hash is a hash - and for a given string should always return the same value. did you try to run his query on your sql ?[/quote]You probably did not reach the last sentence of the paragraph.;-)Mon, 07 Sep 2009 15:19:25 GMTSergiyhttp://www.sqlservercentral.com/Forums/Topic783416-8-1.aspxSergiy - the paragrah you mentioned change nothing. hash is a hash - and for a given string should always return the same value. did you try to run his query on your sql ?Mon, 07 Sep 2009 10:51:26 GMTMarcin Golhttp://www.sqlservercentral.com/Forums/Topic783416-8-1.aspx[quote]which version of SQL Server 2000 you are running ? SP4? later ?[/quote]It's RTM version.Mon, 07 Sep 2009 00:51:44 GMTZahranhttp://www.sqlservercentral.com/Forums/Topic783416-8-1.aspx[quote]which version of SQL Server 2000 you are running ? SP4? later ?[/quote]It's RTM version.Mon, 07 Sep 2009 00:48:44 GMTZahranhttp://www.sqlservercentral.com/Forums/Topic783416-8-1.aspx[quote]which version of SQL Server 2000 you are running ? SP4? later ?[/quote]It's RTM version.Mon, 07 Sep 2009 00:45:42 GMTZahranhttp://www.sqlservercentral.com/Forums/Topic783416-8-1.aspxPlease open BOL on CHECKSUM and read 2nd paragraph of "Remarks".Sun, 06 Sep 2009 22:03:44 GMTSergiyhttp://www.sqlservercentral.com/Forums/Topic783416-8-1.aspxwhich version of SQL Server 2000 you are running ? SP4? later ?Sun, 06 Sep 2009 12:23:23 GMTMarcin Golhttp://www.sqlservercentral.com/Forums/Topic783416-8-1.aspxWhen I execute below SQL statement in SQL server 2000, I get the same value of 128414903 for the CHECKSUM in two different rows with different data. Why is that?[code]DECLARE @checksum TABLE( CustomerNo CHAR(17) ,Address CHAR(40))INSERT INTO @checksumSELECT '00000000014331462','A15 Block No.: 3' UNION ALLSELECT '00000000061051462','F23 Block No.: 5'SELECT CHECKSUM(CustomerNo,Address)FROM @checksum[/code]Sun, 06 Sep 2009 03:47:18 GMTZahran