MySQL synchronization?

Question

I was always wondering if MySQL queries are synchronized - or whatever you call it. For example:

You read a value using SELECT, then you modify it in your code (let's say, PHP on a webserver) and then you UPDATE the table entry. If two processes do this simultaneously, there will obviously be problems.

How is this prevented?

Answer 1

You should read about transaction isolation levels and locks. This is the related link for mysql: http://dev.mysql.com/doc/refman/5.0/en/innodb-transaction-model.html