CAST函数语法规则是:Cast(字段名 as 转换的类型 ),其中类型可以为:

CHAR[(N)] 字符型 
DATE 日期型
DATETIME 日期和时间型
DECIMAL float型
SIGNED int
TIME 时间型

实例1:

表table1

date:2015-11-03 15:31:26

select cast(date as signed) as date from  table1;

结果如下:

date:20151103153126
select cast(date as char) as date from  table1;

结果如下:

date:2015-11-03 15:31:26

实例2:

select cast(date as datetime) as date from  table1;

结果如下:

date:2015-11-03 15:31:26

实例3:

select cast(date as date) as date from  table1;

结果如下:

date:2015-11-03

实例4:

select cast(date as time) as date from  table1;

结果如下:

date:15:31:26

这里date对应日期,time对应时间

实例5:

表table2

num:20

select cast(num as decimal(10, 2)) as num from table2

结果如下:

num:20.00

解释:decimal 数据类型最多可存储 38 个数字,所有数字都能够放到小数点的右边.decimal 数据类型存储了一个准确(精确)的数字表达法;不存储值的近似值.其中10是小数点左边和右边的数字个数之和(不包括小数点),2代表小数点右边的小数位数或数字个数.decimal(10,2)可以存储8位整数2位小数的数字.

05-26 21:55