TIMESTAMPDIFF函数用于计算两个日期的时间差
语法结构
TIMESTAMPDIFF(unit,datetime_expr1,datetime_expr2)
参数说明
【资料图】
unit: 日期比较返回的时间差单位,常用可选值如下:
SECOND:秒
MINUTE:分钟
HOUR:小时
DAY:天
WEEK:星期
MONTH:月
QUARTER:季度
YEAR:年
datetime_expr1: 要比较的日期1
datetime_expr2: 要比较的日期2
TIMESTAMPDIFF函数返回datetime_expr2 - datetime_expr1的结果,其中datetime_expr1和datetime_expr2可以是DATE或DATETIME类型值
示例
-- 相差:25秒 SELECT TIMESTAMPDIFF(SECOND,"2022-04-23 14:57:00","2022-04-23 14:57:25"); -- 相差:5分钟 SELECT TIMESTAMPDIFF(MINUTE,"2022-04-23 15:00:00","2022-04-23 15:05:00"); -- 相差:5小时 SELECT TIMESTAMPDIFF(HOUR,"2022-04-23 11:20:00", "2022-04-23 16:20:00"); -- 相差:2天 SELECT TIMESTAMPDIFF(DAY,"2022-04-23 11:20:00", "2022-04-25 11:20:00"); -- 相差:1星期 SELECT TIMESTAMPDIFF(WEEK,"2022-04-23 11:20:00", "2022-04-30 11:20:00"); -- 相差:1月 SELECT TIMESTAMPDIFF(MONTH,"2022-04-23 11:20:00", "2022-05-30 11:20:00"); -- 相差:1季度 SELECT TIMESTAMPDIFF(QUARTER,"2022-04-23 11:20:00", "2022-07-23 11:20:00"); -- 相差:1年 SELECT TIMESTAMPDIFF(YEAR,"2022-04-23 11:20:00", "2023-04-23 11:20:00");
TIMESTAMPDIFF函数允许其搭配使用的参数datetime_expr1和datetime_expr2具有混合类型
案例
datetime_expr1是DATE类型值,datetime_expr2是DATETIME类型值,TIMESTAMPDIFF函数会将datetime_expr1自动转换成DATETIME类型值(即在日期后面加上时间“00:00:00”)
-- 12 SELECT TIMESTAMPDIFF(HOUR,"2022-04-27","2022-04-27 12:00:00"); -- 12 SELECT TIMESTAMPDIFF(HOUR,"2022-04-27 00:00:00","2022-04-27 12:00:00");
上述两行代码等价,返回的都是相同的结果
TIMESTAMPDIFF函数可以结合日期函数进行搭配使用
-- 可以结合日期函数进行搭配使用 SELECT TIMESTAMPDIFF(SECOND,"2022-04-23", CURRENT_DATE()); SELECT TIMESTAMPDIFF(SECOND,"2022-04-23 15:15:00",NOW()); SELECT TIMESTAMPDIFF(SECOND,"2022-04-23 15:15:00",CURRENT_TIMESTAMP()); -- 上述日期函数补充说明 -- CURRENT_DATE()用于返回当前时间 -- 示例结果:2022-04-27 SELECT CURRENT_DATE(); -- NOW()用于返回当前日期和时间 -- 示例结果:2022-04-27 11:27:28 SELECT NOW(); -- CURRENT_TIMESTAMP()用于返回当前日期和时间 -- 示例结果:2022-04-27 11:30:25 SELECT CURRENT_TIMESTAMP();
练习案例
导入数据
DROP TABLE IF EXISTS Student; CREATE TABLE Student ( SId VARCHAR (10), Sname VARCHAR (10), Sage datetime, Ssex VARCHAR (10) ) ENGINE = InnoDB DEFAULT CHARSET = utf8; INSERT INTO Student(SId,Sname,Sage,Ssex) VALUES("01" , "赵雷" , "1990-01-01" , "男") ,("02" , "钱电" , "1990-12-21" , "男") ,("03" , "孙风" , "1990-05-20" , "男") ,("04" , "李云" , "1990-08-06" , "男") ,("05" , "周梅" , "1991-12-01" , "女") ,("06" , "吴兰" , "1992-03-01" , "女") ,("07" , "郑竹" , "1989-07-01" , "女") ,("08" , "张三" , "2017-12-20" , "女") ,("09" , "李四" , "2017-12-25" , "女") ,("11" , "李四" , "2017-12-30" , "女") ,("12" , "孙七" , "2018-01-01" , "女");
Student表
问题:按照出生日期来算学生年龄,其中当前月日<出生年月的月日,则年龄减一
解题思路
使用NOW()、TIMESTAMPDIFF()函数计算年龄
SELECT *, TIMESTAMPDIFF(YEAR,Sage,NOW())AS age FROM Student;
结果展示:
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