On 2013-05-06, Tim Uckun <timuckun@xxxxxxxxx> wrote: > --047d7b2e4ea07402b004dc034a3b > Content-Type: text/plain; charset=UTF-8 > > Say I have a select like this. > > SELECT * FROM table where field = X OR field = Y limit 1 > > And I have two records one that matches X and one that matches Y will I > always get X because the evaluation will stop after the first clause in the > OR matches? no. there is no guarantee which matching row you will get. Testing may suggest that one answer is preferred but udating the table can change which one. also you may get a different row without updating the table. > What about for IN (X, Y) same deal. > how about if I am doing an update > > UPDATE table1 set x=table2.y where table1.field1 = table2.field1 OR > table1.field2=table2.field2 > > Will it update based on field1 if both fields match? what difference does that make to the result? > Basically I want to know if and how OR shortcuts the evaluation. In a word. "unpredictably". The planner will try to do the cheapest, most useful side first. -- ⚂⚃ 100% natural -- Sent via pgsql-general mailing list (pgsql-general@xxxxxxxxxxxxxx) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-general
