MySQL 8.0 参考手册  / 第 13 章 SQL 语句  / 13.6 复合语句语法  / 13.6.4 存储程序中的变量  /  13.6.4.1 Local Variable DECLARE Statement

13.6.4.1 Local Variable DECLARE Statement

DECLARE var_name [, var_name] ... type [DEFAULT value]

This statement declares local variables within stored programs. To provide a default value for a variable, include a DEFAULT clause. The value can be specified as an expression; it need not be a constant. If the DEFAULT clause is missing, the initial value is NULL.

Local variables are treated like stored routine parameters with respect to data type and overflow checking. See Section 13.1.16, “CREATE PROCEDURE and CREATE FUNCTION Statements”.

Variable declarations must appear before cursor or handler declarations.

Local variable names are not case-sensitive. Permissible characters and quoting rules are the same as for other identifiers, as described in Section 9.2, “Schema Object Names”.

The scope of a local variable is the BEGIN ... END block within which it is declared. The variable can be referred to in blocks nested within the declaring block, except those blocks that declare a variable with the same name.

For examples of variable declarations, see Section 13.6.4.2, “Local Variable Scope and Resolution”.