Hello again, Le 29/07/09 12:21, nha a écrit : > Hello, > > Le 29/07/09 11:48, Gau, Hans-Jürgen a écrit : >> Sorry, it's a lapse by copying and simplification the original version. that >> is correct: >> >> UPDATE table1 t1 >> SET (t1.id) = >> (SELECT t3.id FROM table2 t2,table3 t3, table1 t1 >> WHERE t3.field = t2.field >> AND t2.id = t1.id >> AND t1.id <> t3.id) >> WHERE >> (SELECT t3.id FROM table2 t2,table3 t3, table1 t1 >> WHERE t3.field = t2.field >> AND t2.id = t1.id >> AND t1.id <> t3.id) IS NOT NULL; >> [...] >> the solution brought by Daryl Richter has no effect. > > There is one mistake [...]
To be concrete, a valid version would be: UPDATE table1 t1 SET id = (something) WHERE (anotherthing); > Except this point, the query is valid although I am not sure the result > is always what you may expect [...] To "join" table1 column (assumed: id) to the subquery (sub-select here) expression, table1 recall is not relevant in the subquery. Moreover an alias "t1" is already defined to table1 (at the beginning of the statement). A more suitable version would be: UPDATE table1 t1 SET id = (SELECT t3.id FROM table2 t2, table3 t3 WHERE t3.field = t2.field AND t2.id = t1.id AND t1.id <> t3.id) WHERE (SELECT t3.id FROM table2 t2, table3 t3 WHERE t3.field = t2.field AND t2.id = t1.id AND t1.id <> t3.id) IS NOT NULL; A PostgreSQL-compliant version could also be: UPDATE table1 t1 SET id = t3.id FROM table2 t2, table3 t3 WHERE t3.field = t2.field AND t2.id = t1.id AND t1.id <> t3.id AND t3.id IS NOT NULL; A PostgreSQL-compliant and faster version may be: UPDATE table1 t1 SET id = t3.id FROM table2 t2 INNER JOIN (SELECT t.id, t.field FROM table3 t WHERE t.id IS NOT NULL) t3 ON t3.field = t2.field WHERE t2.id = t1.id AND t3.id <> t1.id; Hoping a satisfying solution is up. -- nha / Lyon / France. -- Sent via pgsql-sql mailing list (pgsql-sql@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-sql
