MySQL 一些重要函数(字符函数)

• 字符连接函数

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select concat('love','-','imooc');

love-imooc

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select concat_ws('','love','imooc','mysql');

loveimoocmysql

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• FORMAT()；数字格式化函数(千分位)

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SELECT FORMAT(12345.12,2);
12,345.12

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• LOWER();字符小写

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SELECT LOWER('MySQL');
mysql

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• UPPER();字符大写

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SELECT UPPER('mysql');
MYSQL

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• LEFT();取左侧字符

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SELECT LEFT('IMOOC',2);
IM

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• RIGHT();取右侧字符

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SELECT RIGHT('IMOOC',2);
OC

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• LENGTH();获取字符长度(包括空格)

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SELECT LENGTH('IMOOC');
5

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• LTRIM();删除前导空格

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SELECT LENGTH(LTRIM(' IMOOC '));
8

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• RTRIM();删除后续空格

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SELECT LENGTH(RTRIM('IMOOC '));
5

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• TRIM();删除空格

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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

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• REPLACE();替换字符函数

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SELECT REPLACE('??MY?SQL???','?','');
MYSQL
SELECT REPLACE('??MY?SQL???','?','!');
!!MY!SQL!!!*

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• SUBSTRING();截取字符串

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SELECT SUBSTRING('IMOOC MYSQL',2,6);
MOOC M
SELECT SUBSTRING('IMOOC MYSQL',-2);
QL

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