函数相关内容。
CONCAT('a','b')
CONCAT_WS('-','a','b')
FORMAT(1234.56,2)
LOWER()
UPPER()
LEFT('MYSQL',2)
RIGHT('MYSQL',2)
LENGTH()
LTRIM()
RTRIM()
TRIM()
例子,删除前导的字符
TRIM(LEADING '?' FROM '??MYSQL???')
结果为
MYSQL???
SUBSTRING('MYSQL','1','2')
结果 MY
[NOT] LIKE
%
任意字符
下划线 _
任意一个字符
REPLACE('??MYSQL??','?','')
CEIL()
FLOOR()
DIV
3 DIV 4
结果 0
MOD
POWER(3,3)
结果 9
ROUND(3.61,2)
TRUNCATE(125.89,0)
结果 125
[NOT] BETWEEN ... AND ...
15 BETWEEN 1 AND 20
[NOT] IN()
10 IN(2,10,20)
IS [NOT] NULL
NOW()
CURDATE()
CURTIME()
DATE_ADD('2014-3-12',INTERVAL 365 DAY)
DATEDIFF('2014-3-12','2013-3-12')
DATE_FORMATE('2014-3-12','%m/%d/$Y')
CONNECTION_ID()
DATABASE()
LAST_INSERT_ID()
USER()
VERSION()
AVG()
COUNT()
MAX()
MIN()
SUM()
MD5()
PASSWORD()
CREATE FUNCTION 函数名
RETURNS
{STRING|INTEGER|REAL|DECIMAL}
函数体;
DROP FUNCTION f1;
CREATE FUNCTION f1()
RETURNS VARCHAR(30)
RETURN DATA_FORMAT(NOW(),'%Y/%m/%d %H:%i:%s')
CREATE FUNCTION f2(num1 SMALLINT UNSIGNED,num2 SMALLINT UNSIGNED)
RETURNS FLOAT(10,2) UNSIGNED
RETURN (num1+num2)/2
函数体若为复合结构,则使用 BEGIAN END
CREATE FUNCTION adduser(username VARCHAR(20))
RETURNS INT UNSIGNED
BEGIN
INSERT test() VALUES(username);
LATEST_INSERT_ID()
END
//