- 字符连接函数
select concat('love','-','imooc');
love-imooc
select concat_ws('','love','imooc','mysql');
loveimoocmysql
- FORMAT()；数字格式化函数(千分位)
SELECT FORMAT(12345.12,2);
12,345.12
- LOWER();字符小写
SELECT LOWER('MySQL');
mysql
- UPPER();字符大写
SELECT UPPER('mysql');
MYSQL
- LEFT();取左侧字符
SELECT LEFT('IMOOC',2);
IM
- RIGHT();取右侧字符
SELECT RIGHT('IMOOC',2);
OC
- LENGTH();获取字符长度(包括空格)
SELECT LENGTH('IMOOC');
5
- LTRIM();删除前导空格
SELECT LENGTH(LTRIM(' IMOOC '));
8
- RTRIM();删除后续空格
SELECT LENGTH(RTRIM('IMOOC '));
5
- TRIM();删除空格
SELECT LENGTH(TRIM('I M O O C '));
5
SELECT TRIM(LEADING'?' FROM '??MYSQL???');--删除from后字符中前面的‘?’
MYSQL???
SELECT TRIM(TRAILING'?' FROM '??MYSQL???');--删除from后字符中后面的‘?’
??MYSQL
SELECT TRIM(BOTH'?' FROM '??MYSQL???');--删除from后字符中后面的‘?’
MYSQL
SELECT TRIM(BOTH'?' FROM '??MY?SQL???');--删除from后字符中前面和后面的‘?’
MY?SQL
- REPLACE();替换字符函数
SELECT REPLACE('??MY?SQL???','?','');
MYSQL
SELECT REPLACE('??MY?SQL???','?','!');
!!MY!SQL!!!*
- SUBSTRING();截取字符串
SELECT SUBSTRING('IMOOC MYSQL',2,6);
MOOC M
SELECT SUBSTRING('IMOOC MYSQL',-2);
QL