When you issue a query, the MySQL Query Optimizer tries to devise an optimal plan for query execution. You can see information about the plan by prefixing the query with EXPLAIN. EXPLAIN is one of the most powerful tools at your disposal for understanding and optimizing troublesome MySQL queries, but it’s a sad fact that many developers rarely make use of it. In this article you’ll learn what the output of EXPLAIN can be and how to use it to optimize your schema and queries.Read moreOriginally published in PHPMaster.com