Table update error - ORA-01407

Question

We have these two tables in Database.
And want to update the first tabel column using second table values.
Can someone help me with what I am doing wrong here?
Please see the query I used below and the error I am getting?
SQL> desc xyz.t_test1
Name Null? Type
SAK_FIN_SCHED NOT NULL NUMBER(9)
SQL> desc dtonse.T_FIN_CYCLE_HISTORY_XWALK
Name Null? Type
SAK_FIN_SCHED NUMBER(9)
NEW_SAK_FIN_SCHED NOT NULL NUMBER(9)
SQL> update xyz.t_test1 a
2 set a.SAK_FIN_SCHED =
3 (select b.NEW_SAK_FIN_SCHED from dtonse.T_FIN_CYCLE_HISTORY_XWALK b
4 where a.sak_fin_sched = b.sak_fin_sched
5 and
6 b.sak_fin_sched is not null);
set a.SAK_FIN_SCHED =
ERROR at line 2:
ORA-01407: cannot update ("XYZ"."T_TEST1"."SAK_FIN_SCHED") to NULL

Answer 1

Your update statement will update all the rows of the table, even the row for which the subquery doesn't return any row, in which case, the update will set the column to null, where you get the error.
You should add a where clause to your "update" to be sure to update only the rows for which the subquery return a result.
update xyz.t_test1 a
set a.SAK_FIN_SCHED = (select b.NEW_SAK_FIN_SCHED
                       from   dtonse.T_FIN_CYCLE_HISTORY_XWALK b
                       where  a.sak_fin_sched = b.sak_fin_sched
                       and    b.sak_fin_sched is not null)
where exists (select 1
              from   dtonse.T_FIN_CYCLE_HISTORY_XWALK b
              where  a.sak_fin_sched = b.sak_fin_sched
              and    b.sak_fin_sched is not null);Nicolas.