Hilary Forbes wrote:
I need to set the value of a field in table A to a value in table B depending
on the existence of the record in table B. So what I have done is
UPDATE tableA set a.val1=b.somefield FROM tableA a, tableB b WHERE
a.key1=b.key1;
Check the EXPLAIN carefully, are you sure the tableA in "UPDATE" is the
same as that in your "FROM" clause. If so, why are you SETting a.val1?
If not, you've probably got an unconstrained join.
--
Richard Huxton
Archonet Ltd
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TIP 9: In versions below 8.0, the planner will ignore your desire to
choose an index scan if your joining column's datatypes do not
match
