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/*
mysql> SELECT species, sex, COUNT(*) FROM Bird
-> WHERE sex IS NOT NULL
-> GROUP BY species, sex;
+---------+------+----------+
| species | sex | COUNT(*) |
+---------+------+----------+
| Bus | m | 2 |
| Car | f | 1 |
+---------+------+----------+
2 rows in set (0.00 sec)
*/
Drop table Bird;
CREATE TABLE Bird (
name VARCHAR(20),
owner VARCHAR(20),
species VARCHAR(20),
sex CHAR(1),
birth DATE,
death DATE
);
INSERT INTO Bird VALUES ('BlueBird','Joe','Car','f','1999-03-30',NULL);
INSERT INTO Bird VALUES ('RedBird','Yin','Bus','m','1979-04-30',1998-01-30);
INSERT INTO Bird VALUES ('RedBird','Yin','Bus','m','1998-01-30',NULL);
/* Or, if you wanted the number of animals per sex only for animals whose
sex is known:
*/
SELECT species, sex, COUNT(*) FROM Bird
WHERE sex IS NOT NULL
GROUP BY species, sex;
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