MySQL函数

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;

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;

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;