mysql - 以下场景需要 SQL 查询

Question

我需要从下表(table1)中获取在同一日期加入(joining_date)部门 dept1 和 dept2 的 emp_id。

emp_id|| department||     joining_date
1     || dept3     ||     01/01/2014
1     || dept2     ||     01/01/2015
1     || dept1     ||     01/01/2015
2     || dept1     ||     01/01/2015
2     || dept2     ||     01/03/2015
3     || dept1     ||     01/02/2015
3     || dept2     ||     01/02/2015
3     || dept3     ||     01/02/2015
4     || dept1     ||     01/01/2014
4     || dept2     ||     01/01/2014
5     || dept1     ||     01/01/2014
5     || dept2     ||     01/01/2015
5     || dept3     ||     01/01/2016
6     || dept1     ||     01/01/2014
6     || dept2     ||     01/01/2014

所以，我应该得到 1,3,4 和 6。

Answer 1

在同一个表上使用 INNER JOIN。

SELECT `first`.* FROM table1 AS first
INNER JOIN table1 AS `second`
        ON `first`.emp_id = `second`.emp_id 
                AND `second`.department = "dept2" 
                AND `second`.joining_date = `first`.joining_date
WHERE first.department = "dept1"

以 dept2 为例，您必须添加 dept3