Use MySQL EXPLAIN for Query Optimization
The EXPLAIN command in MySQL is used to obtain information about how a SELECT, INSERT, UPDATE, or DELETE statement will be executed. It provides information about the query execution plan and the estimated number of rows that will be examined for each table in the query. The data from EXPLAIN can help identify performance bottlenecks and optimize queries for better performance.
The EXPLAIN command works by analyzing the query and determining the most efficient execution plan for it. The query optimizer in MySQL evaluates the available indexes, column statistics, and other factors to determine the best way to retrieve the data requested by the query. The optimizer generates an execution plan based on this analysis, which is then returned as output when you run EXPLAIN.
The output of EXPLAIN includes information such as the join used (e.g., INNER JOIN, LEFT JOIN), the order in which tables are processed, the index used to retrieve data, and the estimated number of rows examined. This information can help you identify performance bottlenecks in your query and optimize it accordingly. For example, if you see a table scan performed instead of an index lookup, you can add an index to the relevant column to improve performance.
In this tutorial, we will: – see why MySQL creates a query plan before each request. – explore a series of examples to show how the EXPLAIN output can be used to identify where MySQL spends time on your query and why. – learn the essential information to look for to spot performance issues.