请假需要层层审批,每次审核存储当前审批人id,需要关联查出对应的名称
方式一:(复杂且性能不佳)
ELECT
absence.id,
(
SELECT
name
FROM
users
WHERE
absence.first_user_id= users.id
) AS firstName,
(
SELECT
name
FROM
users
WHERE
absence.second_user_id= users.id
) AS secondName
FROM
absence
方式二:(关联多次,每次关联一个字段)
SELECT
n.id,
m.name,
q.name
FROM
absence
LEFT JOIN users m ON n.first_user_id= m.id
LEFT JOIN users q ON n.second_user_id = q.id