f7264981   
   From: esquel@sommarskog.se   
      
   migurus (migurus@yahoo.com) writes:   
   > -- we need to change quantity to 0 on row with CID=2   
   > -- app produces this sql:   
   >   
   > update #T   
   > set CID=3,DT='20110210 12:30',QTY=0   
   > where CID=3   
   >   
   > My question - how bad is it? in real tables some colums are indexed,   
   > does it make server to try to modify indexes? Is SQL Server smart not   
   > to update columns whose value was not changed?   
      
   If this reflects the actual SQL - save the temp table - it is bad, but for   
   another reason than you ask about.   
      
   The app should produce parameterised SQL and not inline values, but maybe it   
   does in real life?   
      
   As for updating each column, even if unchanged... Since the application is   
   generating the SQL, it could make the effort to generate an UPDATE statement   
   with only the columns that changes. Then again, that's an extra complexity   
   and it could introduce bugs. And if you have stored procedures, you   
   typically have a procedure that accepts parameters for all columns.   
      
   So, all in all, not too much to be worried about - as long as it is   
   parameterised.   
      
   --   
   Erland Sommarskog, SQL Server MVP, esquel@sommarskog.se   
      
   Books Online for SQL Server 2005 at   
   http://www.microsoft.com/technet/prodtechnol/sql/2005/downloads/books.mspx   
   Books Online for SQL Server 2000 at   
   http://www.microsoft.com/sql/prodinfo/previousversions/books.mspx   
      
   --- SoupGate-Win32 v1.05   
    * Origin: you cannot sedate... all the things you hate (1:229/2)