User Created and Temporary Tables
MEMORY table contents are stored in memory, which is a property that MEMORY tables share with
internal temporary tables that the server creates on the fly while processing queries. However, the two
types of tables differ in that MEMORY tables are not subject to storage conversion, whereas internal
temporary tables are:
• If an internal temporary table becomes too large, the server automatically converts it to on-disk
storage, as described in Section 18.104.22.168, “How MySQL Uses Internal Temporary Tables”.
• User-created MEMORY tables are never converted to disk tables.
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