尝试使用 SQL 从多个表中删除

Question

我们的应用程序中有 4 个表：

• 用户
• 使用会话
• upklist
• 项目共享

最后三个表包含一个名为 session_id 的字段。

在下面的代码中，括号中的部分用于从usession 表中为用户“awpeople”获取所有session_id 值。

问题是我如何将这个结果集读入一个数组并从数组结果中session_id 所在的所有三个表中删除。

代码：

DELETE FROM usession, 
            upklist, 
            projshar 
WHERE  session_id = (SELECT session_id 
                     FROM   usession 
                     WHERE  delete_session_id IS NULL 
                            AND user_id = (SELECT user_id 
                                           FROM   users 
                                           WHERE  REGEXP_LIKE(USER_NAME, 
                                                  'awpeople', 'i'))); 

Answer 1

delete 一次只能处理一个表，因此您需要三个语句：

DELETE FROM upklist 
WHERE  session_id = (SELECT session_id 
                     FROM   usession 
                     WHERE  delete_session_id IS NULL 
                            AND user_id = (SELECT user_id 
                                           FROM   users 
                                           WHERE  REGEXP_LIKE(USER_NAME, 
                                                  'awpeople', 'i'))); 

DELETE FROM projshar 
WHERE  session_id = (SELECT session_id 
                     FROM   usession 
                     WHERE  delete_session_id IS NULL 
                            AND user_id = (SELECT user_id 
                                           FROM   users 
                                           WHERE  REGEXP_LIKE(USER_NAME, 
                                                  'awpeople', 'i'))); 

DELETE FROM usession 
WHERE  session_id = (SELECT session_id 
                     FROM   usession 
                     WHERE  delete_session_id IS NULL 
                            AND user_id = (SELECT user_id 
                                           FROM   users 
                                           WHERE  REGEXP_LIKE(USER_NAME, 
                                                  'awpeople', 'i'))); 

请注意，由于内部查询依赖于usersession，您应该从它last中删除。

Answer 2

多表语法：

删除 [LOW_PRIORITY] [快速] [忽略] tbl_name[.] [, tbl_name[.]] ... FROM table_references [WHERE where_condition]

或者：

删除 [LOW_PRIORITY] [快速] [忽略] FROM tbl_name[.] [, tbl_name[.]] ... 使用 table_references [WHERE where_condition]

这来自 Oracle 的MySQL 5.1 DELETE documentation。

Answer 3

如果usession在session_id上有一个唯一键或主键，并且其他表与它有外键关系，那么您可以从usession中删除该行，并让数据库将其级联到子表。