[SQL] sql-porting-problem oracle to postgresql with UPDATE/IS NOT NULL

[Gau, Hans-Jürgen]

hello list, 
i have some problems with an sql-statement which runs on oracle but not on
postgresql (i want update only if result of SELECT is not empty, the
SELECT-queries are identical):

UPDATE table1 t1 
        SET (t1.id) = 
                (SELECT h.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 h.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; 



thanks, hans