Reading a SQL Execution Plan with EXPLAIN

A slow query rarely needs new hardware; usually it is enough to understand what the database is doing.

Key Points

• Run EXPLAIN before changing anything to see whether the query uses an index or scans the whole table.
• Watch the estimated number of rows processed; a big gap from reality signals stale statistics.
• Add indexes on columns often used in filters and joins, not on every column.
• Measure again after the change and record the result so the improvement can be tracked.

Reading execution plans is a small skill that saves many hours of investigation.

Note: this article is dummy demo content and is not professional advice.