MySQL常用的数据类型及函数_20160920

　  可以参考看下数据类型 http://www.w3school.com.cn/sql/sql_datatypes.asp

 2、函数处理

2.1 对文本（字符串）的处理

　　工作中我们经常需要用到对字符串的处理，取字段的某一部分/拼接/替换/字段长度等等 MySQL中内置许多函数支持这些操作。

　　下面sql代码是工作中用到,整理出来，可以直接在sqlyog中测试

SELECT 
INSTR("abc","c") AS c在字符串abc中位置,
LEFT("abcd",INSTR("abc","c")-1) AS 取abcd字符串c前面字段,
LEFT("abcd",3) AS abcd前3个字符,
RIGHT("abcd",3) AS abcd后3个字符,
CONCAT("aaa","&","111") AS "用&连接aaa和111字符",
CONCAT_WS("-","aaa","111") AS "用-连接aaa和111字符",
REPLACE("abcd","c","111") AS 将c替换为111,#对比insert 
INSERT("abcd",3,2,"111") AS 将字符串abcd第3位后的2位字符替换为111,
LENGTH("abcd") AS abcd英文字符串长度,
LENGTH("中") AS "‘中‘字长度",
LENGTH("-") AS "符号‘-‘长度",
IF(LENGTH(LEFT("123",1))>=3,"是","不是") AS "判断字符‘123‘是不是中文",
IF(LENGTH(LEFT("中文",1))>=3,"是","不是") AS"判断字符‘中文‘是不是中文",
CONCAT(FORMAT(0.3568*100,2),"%") AS 添加百分号保留几位小数

MySQL常用的数据类型及函数_20160920

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