Hello again, Le 27/07/09 16:48, Jamie Lawrence-Jenner a écrit : > Hi There > > Our update statements are as follows > > Update table set col1=x,col2=y where pkid=1; > Update table set col1=x,col2=y where pkid=2; > Update table set col1=x,col2=y where pkid=3; > > Very simple and straight forward. Sometimes there could be as many as 50 > update statements to process. > > Many thanks > > Jamie > [...] > Improvements on the merging UPDATE statements may thence be advised if > some pieces of original statements could be given--without compromising > confidential data. > Thanks for the examples. Comparison between "explain analyze" outputs from the two ways (multiple statements vs. one statement) should help choosing the faster. For the one-statement schema, the rewritten query could be: UPDATE yTable SET col1=x, col2=y WHERE pkID IN (1, 2, 3); Lists of pkID would rather be expressed in terms of enumeration when in WHERE clause. In a more general situation, I would recommand to determine pkIDs list before building UPDATE statement(s) if possible. This hint would surely save runtime. With regards. -- nha / Lyon / France. -- Sent via pgsql-general mailing list (pgsql-general@xxxxxxxxxxxxxx) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-general
