mysql存储过程读书笔记(三): 变量
mysql存储过程读书笔记(3): 变量 1. 变量名: Mysql变量名推荐30个字符以内,命名要有实际意义 2. 声明变量的方式: ???? declare variable_name[,variable_name,....] datatype [default value]; ??? 可以同时定义多个具有相同类型的变量,如果没有default表达
mysql存储过程读书笔记(3): 变量1. 变量名: Mysql变量名推荐30个字符以内,命名要有实际意义
2. 声明变量的方式:
???? declare variable_name[,variable_name,....] datatype [default value];
??? 可以同时定义多个具有相同类型的变量,如果没有default表达式,则默认变量声明之后默认值是Null
?
??? declare 普通变量应该在所有declare cursor语句和declare continue handler语句之前
3.变量类型:
?? int/integer: 32位整数(可以声明为unsigned)
?? bigint: 64位整数(可以声明为unsigned)
?? float: 32位浮点数(可以声明为unsigned)
?? double: 64位浮点数
?? Numeric(precision, scale)/Decimal(precision, scale): 固定小数点数
?? Date: 日期(不包括时间)
?? DateTime: 日期(包括时间)
?? CHAR(length): 固定长度字符串(最长255个)
?? VARCHAR(length):变长字符串(最长255个)
?? BLOB: 二进制大数据(最长64K)
?? TEXT: 字符大数据(最长64K)
??? LONG BLOB:二进制大数据(最长4GB)
??? LONG TEXT: 字符大数据(最长4GB)
?
4.变量赋值:
?? SET variable_name=expression [,variable_name = expression ....];
?? mysql和别的数据库有个比较大的差别就是变量赋值要用SET
?
???
?

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