MySQL LAG/LEAD 问题答案

【问题标题】：MySQL LAG/LEAD issueMySQL LAG/LEAD 问题
【发布时间】：2021-08-19 19:08:50
【问题描述】：

我正在尝试将一些代码从当前主机移动到 GoDaddy，但遇到了 LEAD/LAG 问题。

我的代码中有以下 SQL 语句：

SELECT 
  id, 
  LAG(Clients.id,1) OVER w AS 'lag', 
  LEAD(Clients.id,1) OVER w AS 'lead' 
FROM Clients 
WHERE custno IS NOT NULL 
WINDOW w AS (ORDER BY Clients.id)

在我当前的主机上，完美运行。他们正在运行 10.3.29-MariaDB。

GoDaddy 正在运行 5.6.49-cll-lve MySQL。尝试运行完全相同的查询时出现以下一批错误：

20 errors were found during analysis.

An alias was previously found. (near "w" at position 34)
Unexpected token. (near "w" at position 34)
Unrecognized keyword. (near "AS" at position 36)
Unexpected token. (near "'lag'" at position 39)
Unexpected token. (near "," at position 44)
Unexpected token. (near "LEAD" at position 46)
Unexpected token. (near "(" at position 50)
Unexpected token. (near "Clients" at position 51)
Unexpected token. (near "." at position 58)
Unexpected token. (near "id" at position 59)
Unexpected token. (near "," at position 61)
Unexpected token. (near "1" at position 62)
Unexpected token. (near ")" at position 63)
Unexpected token. (near "OVER" at position 65)
Unexpected token. (near "w" at position 70)
Unrecognized keyword. (near "AS" at position 72)
Unexpected token. (near "'lead'" at position 75)
Unrecognized keyword. (near "AS" at position 129)
Unexpected token. (near "(" at position 132)
Unexpected token. (near ")" at position 152)

有什么建议吗？

【问题讨论】：

标签： mysql mariadb window-functions

【解决方案1】：

您在不支持窗口函数的 MySql 版本中运行此代码（您需要 MySql 8.0+）。

相反，您可以使用相关子查询：

SELECT 
  c.id,
  (SELECT MAX(cc.id) FROM Clients cc WHERE cc.id < c.id) AS `lag`,
  (SELECT MIN(cc.id) FROM Clients cc WHERE cc.id > c.id) AS `lead`  
FROM Clients c 
WHERE c.custno IS NOT NULL

【讨论】：