如果行不存在则先更新然后插入（SQL）而不是先检查行是否存在？

Question

I've always used the method of checking a table to see if a row exists, and then update it with my new data or insert it if it doesn't exist, but it's got me thinking what would be wrong with simply doing an update, if no rows are affected, then do an insert statement, that could potentially speed up my script and put less load on the server.

Anyone foresee any problems with this?

Answer 1

What's wrong with REPLACE?

REPLACE works exactly like INSERT, except that if an old row in the table has the same value as a new row for a PRIMARY KEY or a UNIQUE index, the old row is deleted before the new row is inserted.