这应该为您工作:
SELECT `t1`.`id` , COUNT(`t2`.`id`) AS `count`
FROM `t1` LEFT JOIN `t2` ON `t1`.`id` = `t2`.`id`
GROUP BY `t1`.`id`
左联接确保您拥有t1中的所有行,而COUNT(t2
。id
)使其仅计算t2.id不为null的记录(即-t2中确实存在的记录)
MySQL跨表计数(*)查询帮助
这应该为您工作:
SELECT `t1`.`id` , COUNT(`t2`.`id`) AS `count`
FROM `t1` LEFT JOIN `t2` ON `t1`.`id` = `t2`.`id`
GROUP BY `t1`.`id`
左联接确保您拥有t1中的所有行,而COUNT(t2
。id
)使其仅计算t2.id不为null的记录(即-t2中确实存在的记录)