mysql函数取代相关子查询(Correlated subquery)
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CREATE TABLE `20121105_teacher` (
`teacher_id` int(11) NOT NULL,
`school_id` int(11) NOT NULL,
PRIMARY KEY (`teacher_id`),
KEY `20121105_teacher_idx_school` (`school_id`)
) ENGINE=InnoDB
CREATE TABLE `20121105_teacher` (
`teacher_id` int