SQL:如何在table1的字段中给定的表上建立table1 JOIN table2? [英] SQL: How can we make a table1 JOIN table2 ON a table given in a field in table1?

问题描述

想象一下，我有table1，其中有一个名为"table_name"的列.我使用table1 .table_name将另一个表的名称存储在数据库中.可引用的表都将具有字段"target_id".

Imagine I have table1 which has a column named 'table_name'. I use table1.table_name to store the name of another table in the database. The referenceable tables would all have a field 'target_id.

是否可以在JOIN语句中使用table_name?

Is is possible to use table_name in a JOIN statement?

例如:

SELECT t1.*, t2.* FROM table1 AS t1
                  JOIN table1.table_name AS t2 ON t1.table1_id = t2.target_id

显而易见的解决方案是使用脚本(在我的情况下为C ++)首先获取表名，然后从中构造SQL查询.问题是:我们可以绕过脚本并直接在SQL(MySQL)中执行此操作吗?

The obvious solution is to use the script (C++ in my case) to get the table name first, and construct a SQL query from it. The question is: can we bypass the script and do this directly in SQL (MySQL)?

什么是动态SQL?

推荐答案

唯一的机会是执行2条SQL语句:

The only chance you have is to do 2 SQL statements:

• 选择所需的表名
• 使用此表名动态构建第二查询以获取所需的数据-所需的数据无法直接用SQL进行(听起来像您在某种程度上设计了错误的数据库-但不知道目标是什么很难说.

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