query without records

[chrisrlong]

Uh, because they're different queries.

You obviously have a record where flag = 1 and cod = M, which the second query will find but the first will not.

And I'm assuming you meant:

SELECT A.COD, A.FLAG, B.AREA, B.NUM_ID
FROM TAB A, TAB1 B
WHERE A.ID=B.ID
AND (FLAG=1 OR (FLAG=2 AND COD = 'N'))

- Chris