下面的场景需要SQL查询

Question

我需要从下表（table1）中获取emp_id，该表已在同一日期加入（joined_date）department dept1和dept2。

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＆amp;结果就是这样。

Answer 1

在同一张桌子上使用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"

dept2的示例，你必须添加dept3

Answer 2

您可以使用自联接来获得结果

select distinct d1.emp_id 
from   dept1 d1, 
       dept2 d2 
where  d1.department = 'dept1' 
and    d2.department = 'dept2' 
and    d1.joining_date = d2.joining_date;