假设我有一个格式为的 sql 表:
id INT PRIMARY KEY AUTO_INCREMENT,
action TINYINT NOT NULL,
user_id INT NOT NULL
我想构建一个产生与以下结果相同的查询:
SELECT
(SELECT COUNT(*), action FROM table WHERE action=1 AND user_id=1),
(SELECT COUNT(*), action FROM table WHERE action=2 AND user_id=1),
(SELECT COUNT(*), action FROM table WHERE action=3 AND user_id=1),
...
(SELECT COUNT(*), action FROM table WHERE action=n AND user_id=1)
(1<->n 只是 的范围action
)
但没有所有的冗余和低效率。