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# Using Query Tables

A Query Table is table structure within a StreamBase application used for storing tuple values outside of a stream, which allows the application to share data and maintain state. One or more Query operators can write to or read from an associated Query Table.

Query Tables can be declared to reside in-memory, or on-disk. In the case of memory-resident Query Tables, any data stored in the table at runtime is not saved after the hosting StreamBase Server instance is shut down. By contrast, the data stored in disk-based Query Tables can persist between StreamBase Server sessions if you define a data directory.

A Query Table data construct is always associated with one or more Query operators, which are described in Using the Query Operator.