你如何使用“WITH"?MySQL中的条款?

2021-11-20 00:00:00 common-table-expression mysql mysql-8.0 with-clause subquery-factoring

我正在将所有 SQL Server 查询转换为 MySQL，其中包含 WITH 的查询都失败了.举个例子:

I am converting all my SQL Server queries to MySQL and my queries that have WITH in them are all failing. Here's an example:

WITH t1 AS
(
     SELECT article.*, userinfo.*, category.*
     FROM question
     INNER JOIN userinfo ON userinfo.user_userid = article.article_ownerid
     INNER JOIN category ON article.article_categoryid = category.catid
     WHERE article.article_isdeleted = 0
)
SELECT t1.*
FROM t1
ORDER BY t1.article_date DESC
LIMIT 1, 3

推荐答案

MySQL 8.0 之前的版本 不支持 WITH 子句(SQL Server 中的 CTE；Oracle 中的子查询分解)，因此您只能使用:

MySQL prior to version 8.0 doesn't support the WITH clause (CTE in SQL Server parlance; Subquery Factoring in Oracle), so you are left with using:

  • 临时表
  • 派生表
  • 内联视图(实际上 WITH 子句代表什么 - 它们可以互换)

对该功能的请求可以追溯到 2006 年.

The request for the feature dates back to 2006.

如前所述，您提供了一个糟糕的示例 - 如果您不以任何方式更改列的输出，则无需执行子选择:

As mentioned, you provided a poor example - there's no need to perform a subselect if you aren't altering the output of the columns in any way:

  SELECT * 
    FROM ARTICLE t
    JOIN USERINFO ui ON ui.user_userid = t.article_ownerid
    JOIN CATEGORY c ON c.catid =  t.article_categoryid
   WHERE t.published_ind = 0
ORDER BY t.article_date DESC 
   LIMIT 1, 3

这是一个更好的例子:

SELECT t.name,
       t.num
  FROM TABLE t
  JOIN (SELECT c.id
               COUNT(*) 'num'
          FROM TABLE c
         WHERE c.column = 'a'
      GROUP BY c.id) ta ON ta.id = t.id

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