This documentation is for an older version. If you're using the most current version, select the documentation for that version with the version switch in the upper right corner of the online documentation, or by downloading a newer PDF or EPUB file. How to Avoid Full Table Scans

The output from EXPLAIN shows ALL in the type column when MySQL uses a table scan to resolve a query. This usually happens under the following conditions:

For small tables, a table scan often is appropriate and the performance impact is negligible. For large tables, try the following techniques to avoid having the optimizer incorrectly choose a table scan: