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In MariaDB and before MySQL 5.6, MEMORY was used for internal temporary tables, e.g. to materialize the intermediate results of a query. However, MEMORY tables don't support BLOB and TEXT types, and the user may limit the total size of MEMORY tables and temporary tables. When an internal temporary
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MEMORY is designed to store data that must be accessed quickly, for example caches, or intermediate data that needs to be transformed before storing it to regular tables.
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MEMORY writes table data in-memory. While the table structures are persisted on-disk, the rows in MEMORY tables are lost when MySQL stops.
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Storage engine for the MySQL relational database management systems
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engine is used in place of MEMORY for internal temporary tables.
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and MariaDB. Before the version 4.1 of MySQL it was called Heap.
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implemented improvements to MEMORY to support BLOB and TEXT.
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