1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
|
--
-- 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)
-- errors: ungrouped column references
SELECT a FROM test_having HAVING min(a) < max(a);
ERROR: column "test_having.a" must appear in the GROUP BY clause or be used in an aggregate function
LINE 1: SELECT a FROM test_having HAVING min(a) < max(a);
^
SELECT 1 AS one FROM test_having HAVING a > 1;
ERROR: column "test_having.a" must appear in the GROUP BY clause or be used in an aggregate function
LINE 1: SELECT 1 AS one FROM test_having HAVING a > 1;
^
-- 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;
|
