What is the function of sql_mode in MySQL?

sql_mode is a system variable in MySQL that controls the mode in which MySQL executes and handles SQL statements. Its main functions include:

1. Strict mode: sql_mode can be set to strict mode, such as “STRICT_ALL_TABLES”. In strict mode, MySQL will be more strict in handling data insertion, updating, and deleting operations, returning error messages for illegal data operations to ensure data integrity and consistency.
2. Data validation: Certain options in sql_mode, such as “NO_ZERO_DATE” and “NO_ZERO_IN_DATE”, can prevent inserting or updating fields of date and time types with zero values, avoiding invalid date or time data.
3. Data type conversion: Options in sql_mode, such as “IGNORE_SPACE” and “PIPES_AS_CONCAT”, can alter MySQL’s implicit conversion rules between strings and numbers, thereby affecting the calculation results of expressions.
4. Grammar compatibility: Some options in sql_mode, such as “ANSI_QUOTES” and “ONLY_FULL_GROUP_BY”, can make MySQL syntax stricter to comply with ANSI SQL standards. This can reduce syntax differences that developers may encounter when switching between different database systems.
5. Security: Some options in sql_mode, such as “NO_BACKSLASH_ESCAPES” and “NO_UNSIGNED_SUBTRACTION”, can enhance the security of MySQL by preventing potential security vulnerabilities.

In conclusion, the sql_mode can be altered by setting different options to change the way MySQL operates and processes data, ultimately improving data integrity, consistency, and security.