MYSQL：有没有一种方法可以在触发时创建新表或删除现有表？

Question

Is there a way to create or drop tables in a trigger?

ex: If I have two tables, table1 and table2.

I want to create a trigger on table2, such that whenever table1 gets new inserted value or updates, drop current table2, and then create table3 (a new version of table2 that incorporates the changes in table1)

can I do such thing in Mysql? and what would be the syntax like if there is a way?

Answer 1

No.

https://dev.mysql.com/doc/refman/5.7/en/trigger-syntax.html says:

The trigger cannot use statements that explicitly or implicitly begin or end a transaction, such as START TRANSACTION, COMMIT, or ROLLBACK. (ROLLBACK to SAVEPOINT is permitted because it does not end a transaction.).

All DDL statements cause an implicit COMMIT.

Here's an example:

mysql> create trigger t after insert on mytable for each row
    create table if not exists foo (i int);

ERROR 1422 (HY000): Explicit or implicit commit is not allowed in stored function or trigger.

Your use case sounds like a bad design. INSERT and UPDATE should affect data only, not have side-effects of changing the structure of your table.