# `SQL` Mode

__*SQL_MODE*__

+ The `SQL` mode affects the `SQL` syntax supported by `TiDB` and its behavior for data validation
  + The `SQL` mode is set via the **`SQL_MODE`** system variable
+ `SQL` mode exist at both global level and session level
  + By default, new sessions use global `SQL` mode
  + Users can change the `SQL` mode in their own sessions

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The `TiDB` server uses different `SQL` mode to operate, and different clients can apply different modes. The `SQL` mode defines which `SQL` syntax `TiDB` supports and which data validation checks are performed.