Why Does EXPLAIN's Row Count Differ from COUNT()?

Why the Rows Returned by "EXPLAIN" Differ from "COUNT()"?

The "EXPLAIN" command provides insights into the query execution plan and estimated row count without actually running the query. However, the row count reported by "EXPLAIN" may not always match the actual row count returned by "COUNT()".

This discrepancy occurs because "EXPLAIN" estimates the row count based on table statistics and may not account for certain conditions in the query. For instance, if an index is used in the "WHERE" clause, "EXPLAIN" may estimate the row count as the number of rows scanned using the index, which can be less than the total number of rows in the table.

Additionally, "EXPLAIN" is not always accurate, as it relies on cached table statistics and does not take into account data changes or updates since the statistics were last collected. Therefore, the row count returned by "EXPLAIN" should be considered an estimate and not an exact count.

To determine the exact row count, it is best to use the "COUNT()" function, which scans the entire table and provides an accurate count of all rows meeting the specified criteria.

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