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CREATE TABLE group_test
(a varchar(1),
b varchar(1),
c varchar(1));
INSERT INTO group_test
(a,
b,
c)
VALUES ('a',
'r',
'x'),
('a',
's',
'x'),
('b',
'r',
'x'),
('b',
's',
'y');
4 rows affected
SELECT a,
count(DISTINCT c) #
FROM group_test
GROUP BY a;
| a | # |
|---|---|
| a | 1 |
| b | 2 |
SELECT a,
b,
count(DISTINCT c) #
FROM group_test
GROUP BY a,
b;
| a | b | # |
|---|---|---|
| a | r | 1 |
| b | r | 1 |
| a | s | 1 |
| b | s | 1 |
SELECT count(DISTINCT c) #
FROM group_test;
| # |
|---|
| 2 |