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MySQL 5.5 Reference Manual :: A MySQL 5.5 Frequently Asked Questions :: A.3 MySQL 5.5 FAQ — Server SQL Mode
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A.3. MySQL 5.5 FAQ — Server SQL Mode

Questions

  • 23.3.1: Is the mode dependent on the database or connection?

  • 23.3.2: What is the default server SQL mode when My SQL 5.5 is installed?

  • 23.3.3: Does strict mode impact performance?

  • 23.3.4: Can the rules for strict mode be extended?

  • 23.3.5: How do you determine the server SQL mode?

  • 23.3.6: How many server SQL modes are there?

  • 23.3.7: What are server SQL modes?

Questions and Answers

23.3.1: Is the mode dependent on the database or connection?

A mode is not linked to a particular database. Modes can be set locally to the session (connection), or globally for the server. you can change these settings using SET [GLOBAL|SESSION] sql_mode='modes'.

23.3.2: What is the default server SQL mode when My SQL 5.5 is installed?

By default, no special modes are enabled. See Section 5.1.8, “Server SQL Modes”, for information about all available modes and MySQL's default behavior.

23.3.3: Does strict mode impact performance?

The intensive validation of input data that some settings requires more time than if the validation is not done. While the performance impact is not that great, if you do not require such validation (perhaps your application already handles all of this), then MySQL gives you the option of leaving strict mode disabled. However — if you do require it — strict mode can provide such validation.

23.3.4: Can the rules for strict mode be extended?

When we refer to strict mode, we mean a mode where at least one of the modes TRADITIONAL, STRICT_TRANS_TABLES, or STRICT_ALL_TABLES is enabled. Options can be combined, so you can add additional restrictions to a mode. See Section 5.1.8, “Server SQL Modes”, for more information.

23.3.5: How do you determine the server SQL mode?

You can set the default SQL mode (for mysqld startup) with the --sql-mode option. Using the statement SET [GLOBAL|SESSION] sql_mode='modes', you can change the settings from within a connection, either locally to the connection, or to take effect globally. You can retrieve the current mode by issuing a SELECT @@sql_mode statement.

23.3.6: How many server SQL modes are there?

Each mode can be independently switched on and off. See Section 5.1.8, “Server SQL Modes”, for a complete list of available modes.

23.3.7: What are server SQL modes?

Server SQL modes define what SQL syntax MySQL should support and what kind of data validation checks it should perform. This makes it easier to use MySQL in different environments and to use MySQL together with other database servers. The MySQL Server apply these modes individually to different clients. For more information, see Section 5.1.8, “Server SQL Modes”.