I have two tables that are identical to each other `t1` and `t2`, but `t2` has more data than `t1`.
I'm using this query to insert the missing data from `t2` to `t1`.

```
insert into t1
select * from t2
where not exist ( select * from t1
                  where t1.key1 = t2.key1
                  and t1.key2 = t2.key2)

```

When this query is run I get the: ORA-00001 Unique constraint (string.string) violated error.

The two tables have `key1` and `key2` as keys.

Since the only constraint is the two keys I don't understand why I'm getting that error.

EDIT: I noticed now in "Indexes" that there are 2 constraints both are of type unique.

The first one is: key1, random\_column
The second one is: key2

sorry for the inconvenience.