Question

我有一个查询（我在下面显示）生成以下结果集（这会继续增加53,000条记录）

+--------+---------+--------+--------+------------+------------+
| emp_no | counter | emp_no | salary | from_date  | to_date    |
+--------+---------+--------+--------+------------+------------+
|  10001 |       1 |  10001 |  60117 | 1986-06-26 | 1987-06-26 |
|  10001 |       1 |  10001 |  62102 | 1987-06-26 | 1988-06-25 |
|  10001 |       1 |  10001 |  66074 | 1988-06-25 | 1989-06-25 |
|  10001 |       1 |  10001 |  84917 | 1999-06-23 | 2000-06-22 |
|  10001 |       1 |  10001 |  85112 | 2000-06-22 | 2001-06-22 |
|  10001 |       1 |  10001 |  85097 | 2001-06-22 | 2002-06-22 |
|  10001 |       1 |  10001 |  88958 | 2002-06-22 | 9999-01-01 |
|  10002 |       2 |  10002 |  65828 | 1996-08-03 | 1997-08-03 |
|  10002 |       2 |  10002 |  65909 | 1997-08-03 | 1998-08-03 |
|  10002 |       2 |  10002 |  67534 | 1998-08-03 | 1999-08-03 |
|  10002 |       2 |  10002 |  69366 | 1999-08-03 | 2000-08-02 |
|  10002 |       2 |  10002 |  71963 | 2000-08-02 | 2001-08-02 |
|  10002 |       2 |  10002 |  72527 | 2001-08-02 | 9999-01-01 |
...

如果员工编号X可以存储多个工资，我用来获取此套件的查询是：

SELECT * FROM (
    SELECT dept_emp.emp_no, @counter := @counter+1 AS counter 
    FROM (select @counter:=0) AS initvar, dept_emp) 
AS employeeFilter 
LEFT JOIN(salaries) 
ON (salaries.emp_no = employeeFilter.emp_no) 
WHERE counter <= (25/100 * @counter) LIMIT 100;

我希望为每个唯一的emp_no获取一行，即最近的工资行（基于to_date字段）。

+--------+---------+--------+--------+------------+------------+
| emp_no | counter | emp_no | salary | from_date  | to_date    |
+--------+---------+--------+--------+------------+------------+
|  10001 |       1 |  10001 |  88958 | 2002-06-22 | 9999-01-01 |
|  10002 |       2 |  10002 |  72527 | 2001-08-02 | 9999-01-01 |

@counter实现对于这个问题并不是很重要，但它确实需要保留在该查询中，因为我希望最终构建一个查询，这将产生削减25％的成本部门和@counter变量允许我按百分比限制结果。

尝试使用DISTINCT select DISTINCT (emp_no)，但我不是最好用这样的东西，这只会引起更多问题。

Answer 1

通过附加具有聚合函数（MAX）的子查询来使用此语句。

SELECT * FROM (
    SELECT dept_emp.emp_no, @counter := @counter+1 AS counter 
    FROM (select @counter:=0) AS initvar, dept_emp) 
AS employeeFilter 
LEFT JOIN(salaries) 
ON (salaries.emp_no = employeeFilter.emp_no) 
WHERE counter <= (25/100 * @counter) AND
    (salaries.emp_no, salaries.to_date) IN 
        (SELECT sal.emp_no, MAX(sal.to_date) 
         FROM salaries sal
         WHERE sal.emp_no = salaries.emp_no)
LIMIT 100;

Answer 2

您可以使用JOIN创建与ROW_NUMBER相同的逻辑：

SELECT * FROM (
    SELECT t.*,count(*) as rnk
    FROM (YourQuery/table) t
    INNER JOIN (YourQuery/table) s
    ON (t.emp_no = s.emp_no AND t.from_date <= s.from_date))
WHERE rnk = 1

或使用相关查询：

SELECT * FROM (YourQuery) t
WHERE from_date = (select max(s.from_date) 
                   FROM (YourQuery) s
                   WHERE s.emp_no = t.emp_no)

Answer 3

<a href="#one">First</a>
<a href="#two">Second</a>
<a href="#three">Third</a>

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选择一组结果中的最新日期

3 个答案: