InstantForum.NET v2.9.0SQLServerCentralhttp://www.sqlservercentral.com/Forums/notifications@sqlservercentral.comWed, 19 Jun 2013 00:36:45 GMT20http://www.sqlservercentral.com/Forums/Topic1429334-1292-1.aspxIf you had added PERSISTED when adding the computed column there is a possibility you might still be waiting for that complete :-)Tue, 12 Mar 2013 05:48:37 GMTopc.threehttp://www.sqlservercentral.com/Forums/Topic1429334-1292-1.aspxThat makes perfect sense. Thanks for the clarification.Mon, 11 Mar 2013 10:20:11 GMTAbu Dinahttp://www.sqlservercentral.com/Forums/Topic1429334-1292-1.aspxIf I were to guess from my limited knowledge of Hashbytes that this is treated like a computed column and doesn't actually store anything, only returning a value on select.Mon, 11 Mar 2013 10:17:42 GMTErin Ramsayhttp://www.sqlservercentral.com/Forums/Topic1429334-1292-1.aspxI have a table with 56 million rows. I performed the following operation:ALTER TABLE MyBigTable ADD NewHashColumn AS HASHBYTES('SHA2_512', Column1+Column2+Column3)The operation took a fraction of a second to complete. How is this possioble?! I mean can SQL Server really generate so many hash keys in such space of time?!I'm guessing that the table was already in memory and all this operation took place in memory? Will the next checkpoint write the actual hash codes to the disk?Mon, 11 Mar 2013 09:16:19 GMTAbu Dina