在MySQL中加入同一个表? [英] join with same table in mysql?

问题描述

我有下表，每个员工都有一个经理，如果一个人是他自己的经理，而managerid字段为null，我希望emid name and manager id因为结果表名称是employee

Im having the following table , each employee have a manager, if a guy is his own manager den the managerid field is null, i want emid name and manager id as result table name is employee

emid name managerid
1    raj  null
2    ram   1
3    ravi   null
4    arvind  3
5    rithu   2

我希望结果为

emid name managername
1    raj  raj
2    ram   raj
3    ravi   ravi
4    arvind  ravi
5    rithu   ram

推荐答案

SELECT e1.emid, e1.name, COALESCE(e2.name, e1.name) AS managername
    FROM employee e1
        LEFT JOIN employee e2
            ON e1.managerid = e2.emid

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