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- --
- -- SELECT_HAVING
- --
- -- load test data
- CREATE TABLE test_having (a int, b int, c char(8), d char);
- INSERT INTO test_having VALUES (0, 1, 'XXXX', 'A');
- INSERT INTO test_having VALUES (1, 2, 'AAAA', 'b');
- INSERT INTO test_having VALUES (2, 2, 'AAAA', 'c');
- INSERT INTO test_having VALUES (3, 3, 'BBBB', 'D');
- INSERT INTO test_having VALUES (4, 3, 'BBBB', 'e');
- INSERT INTO test_having VALUES (5, 3, 'bbbb', 'F');
- INSERT INTO test_having VALUES (6, 4, 'cccc', 'g');
- INSERT INTO test_having VALUES (7, 4, 'cccc', 'h');
- INSERT INTO test_having VALUES (8, 4, 'CCCC', 'I');
- INSERT INTO test_having VALUES (9, 4, 'CCCC', 'j');
- SELECT b, c FROM test_having
- GROUP BY b, c HAVING count(*) = 1 ORDER BY b, c;
- b | c
- ---+----------
- 1 | XXXX
- 3 | bbbb
- (2 rows)
- -- HAVING is effectively equivalent to WHERE in this case
- SELECT b, c FROM test_having
- GROUP BY b, c HAVING b = 3 ORDER BY b, c;
- b | c
- ---+----------
- 3 | BBBB
- 3 | bbbb
- (2 rows)
- SELECT lower(c), count(c) FROM test_having
- GROUP BY lower(c) HAVING count(*) > 2 OR min(a) = max(a)
- ORDER BY lower(c);
- lower | count
- -------+-------
- bbbb | 3
- cccc | 4
- xxxx | 1
- (3 rows)
- SELECT c, max(a) FROM test_having
- GROUP BY c HAVING count(*) > 2 OR min(a) = max(a)
- ORDER BY c;
- c | max
- ----------+-----
- XXXX | 0
- bbbb | 5
- (2 rows)
- -- test degenerate cases involving HAVING without GROUP BY
- -- Per SQL spec, these should generate 0 or 1 row, even without aggregates
- SELECT min(a), max(a) FROM test_having HAVING min(a) = max(a);
- min | max
- -----+-----
- (0 rows)
- SELECT min(a), max(a) FROM test_having HAVING min(a) < max(a);
- min | max
- -----+-----
- 0 | 9
- (1 row)
- -- the really degenerate case: need not scan table at all
- SELECT 1 AS one FROM test_having HAVING 1 > 2;
- one
- -----
- (0 rows)
- SELECT 1 AS one FROM test_having HAVING 1 < 2;
- one
- -----
- 1
- (1 row)
- -- and just to prove that we aren't scanning the table:
- SELECT 1 AS one FROM test_having WHERE 1/a = 1 HAVING 1 < 2;
- one
- -----
- 1
- (1 row)
- DROP TABLE test_having;
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