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概述

MySQL函数是MySQL数据库中的一种特殊的语法，用于对数据进行处理和计算，本文介绍了MySQL函数的基本语法和常用操作。

文本处理

函数	说明	示例
UPPER	将字符串转换为大写	SELECT UPPER('hello') AS Uppercase;
LOWER	将字符串转换为小写	SELECT LOWER('WORLD') AS Lowercase;
LENGTH	获取字符串的长度	SELECT LENGTH('Moonshot') AS Length;
CONCAT	拼接字符串	SELECT CONCAT('Hello', ' ', 'World') AS ConcatenatedString;
SUBSTRING	截取字符串	SELECT SUBSTRING('Moonshot', 1, 5) AS Substring;
REPLACE	替换字符串	SELECT REPLACE('Moonshot', 'Moon', 'Star') AS ReplacedString;

日期和时间处理

函数	说明	示例
NOW	获取当前日期和时间	SELECT NOW() AS CurrentDateTime;
CURDATE	获取当前日期	SELECT CURDATE() AS CurrentDate;
CURTIME	获取当前时间	SELECT CURTIME() AS CurrentTime;
DATE	获取日期部分	SELECT DATE('2024-09-18 08:23:45') AS DatePart;
TIME	获取时间部分	SELECT TIME('2024-09-18 08:23:45') AS TimePart;
YEAR	获取年份	SELECT YEAR(CURDATE()) AS Year;
MONTH	获取月份	SELECT MONTH(CURDATE()) AS Month;
DAY	获取天数	SELECT DAY(CURDATE()) AS Day;
HOUR	获取小时	SELECT HOUR(CURTIME()) AS Hour;
MINUTE	获取分钟	SELECT MINUTE(CURTIME()) AS Minute;
SECOND	获取秒数	SELECT SECOND(CURTIME()) AS Second;
WEEKDAY	获取星期	SELECT WEEKDAY(CURDATE()) AS Weekday;
DAYOFYEAR	获取年的第几天	SELECT DAYOFYEAR(CURDATE()) AS DayOfYear;
WEEK	获取年的第几周	SELECT WEEK(CURDATE()) AS WeekOfYear;
DATEDIFF	计算日期差	SELECT DATEDIFF(CURDATE(), '2024-01-01') AS DateDifference;
DATE_FORMAT	日期格式化	SELECT DATE_FORMAT(CURDATE(), '%Y-%m-%d') AS DateFormat;
DATE_ADD	日期加	SELECT DATE_ADD(CURDATE(), INTERVAL 1 DAY) AS DateAdd;
DATE_SUB	日期减	SELECT DATE_SUB(CURDATE(), INTERVAL 1 DAY) AS DateSub;

数值处理

函数	说明	示例
ABS	绝对值	SELECT ABS(-10) AS AbsoluteValue;
CEIL	向上取整	SELECT CEIL(3.14) AS CeilValue;
FLOOR	向下取整	SELECT FLOOR(3.14) AS FloorValue;
ROUND	四舍五入	SELECT ROUND(3.14) AS RoundValue;
RAND	随机数	SELECT RAND() AS RandomNumber;
SQRT	平方根	SELECT SQRT(16) AS SquareRoot;
POW	幂运算	SELECT POW(2, 3) AS Power;
MOD	取模运算	SELECT MOD(10, 3) AS Modulus;

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