是否有可能用另一个查询的结果替换查询中的 MySql 表名

Question

How to use select result of one table as table name in subquery. Is there any hack about that in MySql 5.6?

Answer 1

No, the way SQL works is that all identifiers (eg table names, column names) and SQL syntax must be fixed at the time the query is prepared -- which is before it begins reading any data.

Therefore no data the query reads during the execution phase can change the table or other fixed elements of the query.

It would be like writing a function in your application where you wanted the return value of the function to determine which function to call.

The workaround is that you have to do this in two steps. The first step is what you're expecting to run as a subquery. It returns information you can use to choose which table to query in the main query. But you have to fetch this from the first query before you prepare the second query.