Oracle SQL correlated update

Question

I got three tables:

t1.columns: a,c
t2.columns: a,b
t3.columns: b,c,d

Now what I want is to update t1.c with t3.d. But I can\'t just update t1

Answer 1

You have a subquery that is returning more than one row. Use rownum to get just one row:

UPDATE table1 t1
   SET t1.c = (select d
               from (select t3.d
                     from table2 t2 join table3 t3
                          on t2.b = t3.b 
                     where t1.a = t2.a
                    ) t
                where rownum = 1
               )                                
 WHERE EXISTS ( SELECT 1 FROM table2 t2, table3 t3 WHERE t1.c = t3.c and t1.a = t2.a);