Question

我试图在与INNER JOIN相同的查询中使用内部GROUP BY和ORDER BY命令，但它没有发生。

我有员工表：

+------------+------+
| id | fname | lname|         |
+------------+------+
| 11 | ABCD  | XHME |
| 12 | CDEF  | LMOP |
| 13 | MNOP  | DDDD |
+---------+---------+

emp_details表

+----+--------+-----------+--------------+--------------+-------+
| id | emp_id | company   | joining_date | Leaving_date | salary|
+---------+---------+--------------------+--------------|-------+
| 1 |   11    | Company 1 | 1999-01-03   | 2001-07-08   | 12000 |
| 2 |   11    | Company 2 | 2005-07-09   | 2007-01-31   | 16000 |
| 3 |   11    | Company 3 | 2002-04-07   | 2015-04-28   | 23000 |
| 4 |   12    | Companyxyz| 2000-10-12   | 2004-03-09   | 17000 |
| 5 |   12    | TestCom   | 2010-10-10   | 2014-10-10   | 35000 | 
+---+---------+-----------+--------------+--------------+-------+

我想像这样显示

+------------+--------------+------------------+
| User Name  | Last Company | Last Drawn Salary|
+------------+--------------+------------------+
| ABCD XMHE  | Company 3    |     23000        |
| LDEF LMOP  | TestCom      |     35000        |
+------------+--------------+------------------+

我的查询就像这样

SELECT employee.id AS eid, employee.employer_id, employee.fname, employee.lname, emp_details.id as emid, emp_details.emp_id, emp_details.company, emp_details.joining_date, emp_details.leaving_date, emp_details.last_drawn_salary 
FROM employee
INNER JOIN emp_details ON employee.id = emp_details.emp_id 
WHERE employee.pan='".$pan."' 
GROUP BY emp_details.emp_id 
ORDER BY emp_details.id DESC

我也尝试使用这样的max(emp_details.id) as emid，但仍然只显示第一个插入的列。这是什么问题？

Answer 1

对于您显示的结果，您可以使用带有emp_details emp_id

组的子查询

    SELECT 
      employee.id AS eid
    , employee.employer_id
    , employee.fname
    , employee.lname
    , emp_details.id as emid
    , emp_details.emp_id
    , emp_details.company
    , emp_details.joining_date
    , emp_details.leaving_date
    , emp_details.last_drawn_salary 
    FROM employee
    INNER JOIN emp_details ON employee.id = emp_details.emp_id
    WHERE (emp_details, emp_id)  in  ( select  max(emp_detail), emp_id  FROM   emp_details group by emp_id)
    ORDER BY emp_details.id DESC

Answer 2

你可以在它的头上翻转它并首先在emp_details表中查找以允许你使用DISTINCT，然后加入员工，如下所示：

SELECT CONCAT_WS(' ', employee.fname, employee.lname) AS `User Name`,
emp_details.company AS `Last Company`,
emp_details.salary,
DISTINCT(emp_details.emp_id)
FROM emp_details
INNER JOIN employee ON employee.id = emp_details.emp_id
## Add your WHERE statement here if you need it
ORDER BY emp_details.Leaving_date DESC

CONCAT_WS允许您连接多个列。 See the documentation for CONCAT_WS for more information

如果有效，请告诉我，我没有机会对其进行测试。

Answer 3

final answer

   select CONCAT_WS(' ', e.fname, e.lnam) AS `User Name`,ed.company as last_company,esd.salary as max_salery from (select max(Leaving_date) as Leaving_date,emp_id from emp_details group by emp_id) eld INNER JOIN emp_details ed on ed.Leaving_date=eld.Leaving_date and ed.emp_id=eld.emp_id INNER JOIN (select max(salary) as salary,emp_id from emp_details group by emp_id) esd on ed.emp_id=esd.emp_id inner join Employee e on e.id = ed.emp_id;
    +-----------+--------------+------------+
    | User Name | last_company | max_salery |
    +-----------+--------------+------------+
    | ABCD XHME | Company 3    |      23000 |
    | CDEF LMOP | TestCom      |      35000 |
    +-----------+--------------+------------+
    2 rows in set (0.00 sec)


Step By Step Answer 


select max(Leaving_date),emp_id from emp_details group by emp_id;
+-------------------+--------+
| max(Leaving_date) | emp_id |
+-------------------+--------+
| 2015-04-28        |     11 |
| 2014-10-10        |     12 |
+-------------------+--------+
2 rows in set (0.00 sec)

select max(salary),emp_id from emp_details group by emp_id;
+-------------+--------+
| max(salary) | emp_id |
+-------------+--------+
|       23000 |     11 |
|       35000 |     12 |
+-------------+--------+
2 rows in set (0.00 sec)

select * from (select max(Leaving_date) as Leaving_date,emp_id from emp_details group by emp_id) eld INNER JOIN emp_details ed on ed.Leaving_date=eld.Leaving_date and ed.emp_id=eld.emp_id;
+--------------+--------+------+--------+------------+--------------+--------------+--------+
| Leaving_date | emp_id | id   | emp_id | company    | joining_date | Leaving_date | salary |
+--------------+--------+------+--------+------------+--------------+--------------+--------+
| 2015-04-28   |     11 |    3 |     11 | Company 3  | 2002-04-07   | 2015-04-28   |  23000 |
| 2014-10-10   |     12 |    5 |     12 | TestCom    | 2010-10-10   | 2014-10-10   |  35000 |
+--------------+--------+------+--------+------------+--------------+--------------+--------+
2 rows in set (0.00 sec)

select ed.emp_id,ed.company as last_company,esd.salary as max_salery from (select max(Leaving_date) as Leaving_date,emp_id from emp_details group by emp_id) eld INNER JOIN emp_details ed on ed.Leaving_date=eld.Leaving_date and ed.emp_id=eld.emp_id INNER JOIN (select max(salary) as salary,emp_id from emp_details group by emp_id) esd on ed.emp_id=esd.emp_id;
+--------+--------------+------------+
| emp_id | last_company | max_salery |
+--------+--------------+------------+
|     11 | Company 3    |      23000 |
|     12 | TestCom      |      35000 |
+--------+--------------+------------+
2 rows in set (0.00 sec)

使用groupby和order by with inner join

3 个答案: