Need help regarding updating one table from another

[gandolf989]

Hmm, Where is the "WHERE" clause?

I composed some sample code to show that the update statement works and highlighted the WHERE clause.

SQL> select version from v$instance;

VERSION
-----------------
9.2.0.7.0

SQL> CREATE TABLE t1
    AS SELECT rownum pkey, rownum val
         FROM dba_objects
        WHERE rownum < 11;
  2    3    4
Table created.

CREATE TABLE t2
    AS SELECT rownum pkey, rownum*2 val
         FROM dba_objects
        WHERE rownum < 11;
SQL>   2    3    4
Table created.

SQL> UPDATE t1
   SET val =
     ( SELECT val
         FROM t2
        WHERE t2.pkey = t1.pkey );
  2    3    4    5
10 rows updated.

SQL> COMMIT;

SELECT *
  FROM t1;

Commit complete.

SQL>   2
      PKEY        VAL
---------- ----------
         1          2
         2          4
         3          6
         4          8
         5         10
         6         12
         7         14
         8         16
         9         18
        10         20

10 rows selected.