How Do I Set and Manage Global `sql_mode` in MySQL?

Setting Global sql_mode in MySQL

In MySQL, sql_mode defines the default behavior of the database server. Setting sql_mode globally applies the configured mode to all subsequent connections and sessions. This differs from setting sql_mode per session, which affects only the current connection.

When encountering errors while setting sql_mode globally, it's important to review the syntax. The correct way to set multiple modes in a global context is:

SET GLOBAL sql_mode = 'NO_BACKSLASH_ESCAPES', 'STRICT_TRANS_TABLE', 'NO_AUTO_CREATE_USER', 'NO_ENGINE_SUBSTITUTION'

Advantages of Global and Session Modes

• Global Modes:

  • Enforce consistent behavior across all connections, ensuring a standardized database environment.
  • Avoid the need for individual users or applications to set specific modes per session.

• Session Modes:

  • Provide flexibility to override global settings for specific tasks or users.
  • Allow temporary modifications to sql_mode without affecting other sessions.

Preferred Setting

The preferred setting depends on the application and environment. If consistent behavior is desired across the board, setting sql_mode globally is recommended. However, if specific session requirements arise, session modes provide the necessary flexibility.

Setting Global sql_mode Permanently

To make global sql_mode changes permanent, they need to be configured in the MySQL configuration file (e.g., /etc/mysql/my.cnf on Linux). In the [mysqld] section, add or modify the sql_mode option. For example:

[mysqld]
sql_mode = NO_BACKSLASH_ESCAPES, STRICT_TRANS_TABLES, NO_ENGINE_SUBSTITUTION

For newer versions of MySQL (e.g., 5.7.8 or above), the sql_mode setting may require a hyphen instead of an underscore and double quotes:

[mysqld]
sql-mode="STRICT_TRANS_TABLES,NO_ENGINE_SUBSTITUTION"

Always consult the MySQL documentation for the appropriate syntax based on the MySQL version in use.

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