问题
I was suggested to do this
SELECT table_schema, table_name FROM information_schema.tables
WHERE table_schema = 'mydb' AND table_name='ApprovePost';
However it is not reliable and cause me errors on several versions of mysql on windows and linux.
Maybe there is another way. Does anyone know?
This issue is I can do create table if not exists but I do a second pass to add the FK constraint. In my SQL dump I see > 130 contains on a single table. The table only has 6 columns, only two of these need constrains. The constrains keep building and building every time I restart the Apache server or whenever mono feels the need to call my global init method in my webapp.
回答1:
Looks like you need to use the FLUSH TABLES command for the INFORMATION_SCHEMA.TABLES to reflect existing tables.
Reference:
- TABLE CACHE
回答2:
If your only actual problem now is recreating the foreign key constantly (aside from a possibly broken MySQL install considering your other troubles), why not:
1) give it a constraint symbol (should be unique in database) and let the adding fail silently / catch 'em?
ALTER TABLE tbl ADD CONSTRAINT only_one_please FOREIGN KEY (columnname) ...
2) or better yet, add the foreign key clause in your create table in the first place?
As for the original question: I know no reason why this should happen, and I cannot recreate it. Selecting from information_schema is afaik quite the preferred way of checking this, and hasn't failed me yet. Aside from a brute force check like SELECT * FROM tablename LIMIT 0; and checking for errors, you first might want to check for any other caching mechanisms besides MySQL's query cache, and if they're not there / not the problem, perhaps try a SELECT SQL_NO_CACHE table_schema, table_name FROM information_schema.tables.
来源：https://stackoverflow.com/questions/3240164/how-do-i-detect-if-a-table-exist-mysql