Problems with MERGE INTO statement

Hi,

I'm playing with the merge into statement but got stuck on this easy thing:

stat_at_DEV> CREATE TABLE t1 (id NUMBER, value NUMBER);

Table created.

stat_at_DEV>
stat_at_DEV> MERGE INTO t1
  2 USING t1 ON (id = 1)
  3 WHEN MATCHED THEN UPDATE SET value = 20   4 WHEN NOT MATCHED THEN INSERT (id, value) VALUES (1, 20);   WHEN MATCHED THEN UPDATE SET value = 20   *
ERROR at line 3:
ORA-00918: column ambiguously defined

I thought that would be an easy example. I want to add a entry into t1 but do not know if there is already an entry with id=1. So I thought using merge could save me the query in the beginning. Maybe someone could point me to the problem.

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Matthias Wirtz  -  Norfolk, USA