mysql - 为什么 MySQL 中没有无限跟随？

Question

为什么我不能在 MySQL 中使用无限跟随？

我可以使用 unbounded preceding 而不会对同一查询产生任何问题。

SELECT deptno,
       ENAME
       SAL,
       HIREDATE,
       last_value(HIREDATE) OVER (
           PARTITION BY deptno
           ORDER BY HIREDATE
           ROWS UNBOUNDED FOLLOWING
       )
FROM emp2
ORDER BY DEPTNO, HIREDATE;

输出:

[42000][1064] You have an error in your SQL syntax; check the manual that corresponds to your MySQL server version for the right syntax to use near
FOLLWOING ) FROM emp2 ORDER BY DEPTNO, HIREDATE at line 2

Answer 1

有两种方法可以使用 window frame specification :

• 显式指定下帧边界并隐式使用当前行作为上限
• 明确指定下限和上限

查看手册:

The frame_extent value indicates the start and end points of the frame. You can specify just the start of the frame (in which case the current row is implicitly the end) or use BETWEEN to specify both frame endpoints

你要写的是这样的:

SELECT 
  deptno, ename, sal, hiredate,
  last_value (hiredate) OVER (
    PARTITION BY deptno 
    ORDER BY hiredate 
    ROWS BETWEEN UNBOUNDED PRECEDING AND UNBOUNDED FOLLOWING
  )
FROM emp2
ORDER BY deptno, hiredate