Mysql 数据类型转换详解

1 概述

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MySQL数据类型转换

被动转换

加号运算符

字符串连接函数

1+'1' -- 2

concat(1,'1') -- 11

主动转换

convert函数转换

cast函数转换

日期时间互转函数

convert(expr, type)

cast(expr as type)

str_to_date

date_format

2 类型转换

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char

date、time、datetime

date_format()

signed、unsigned、decimal(n,m)

数值

字符

日期

select -- 数值 -> 字符-- char(n) n 个长度的字符，超过截取convert(2022, char(3)) c1, -- 202convert(2022, char(4)) c2, -- 2022convert(2022, char(5)) c3, -- 2022-- 字符 -> 数值convert('-12.56', SIGNED) s1, -- -12 有符号整数convert('12.56', UNSIGNED) u1, -- 12 无符号整数convert('12.56', decimal(3, 1)) dc1, -- 12.6 浮点数，四舍五入-- 字符 -> 日期convert('2021-05-20 13:14:00', datetime) d1, -- 日期+时间convert('2021-05-20 13:14:00', date) d2, -- 仅日期convert('2021-05-20 13:14:00', time) d3, -- 仅时间str_to_date('2021-05-20 13:14:00', '%Y-%m-%d %H:%i:%S') d4,str_to_date(now(), '%Y-%m-%d') d5, -- 日期截取-- 日期 -> 字符convert(now(), char) c4,date_format(now(), '%Y-%m-%d %H:%i:%S') c5 -- 注意大小写from dual;