CHARSET(str) //返回字串字符集
CONCAT (string2 [,... ]) //連接字串
INSTR (string ,substring ) //返回substring首次在string中出現(xiàn)的位置,不存在返回0
LCASE (string2 ) //轉(zhuǎn)換成小寫
LEFT (string2 ,length ) //從string2中的左邊起取length個字符
LENGTH (string ) //string長度
LOAD_FILE (file_name ) //從文件讀取內(nèi)容
LOCATE (substring , string [,start_position ] ) 同INSTR,但可指定開始位置
LPAD (string2 ,length ,pad ) //重復(fù)用pad加在string開頭,直到字串長度為length
LTRIM (string2 ) //去除前端空格
REPEAT (string2 ,count ) //重復(fù)count次
REPLACE (str ,search_str ,replace_str ) //在str中用replace_str替換search_str
RPAD (string2 ,length ,pad) //在str后用pad補充,直到長度為length
RTRIM (string2 ) //去除后端空格
STRCMP (string1 ,string2 ) //逐字符比較兩字串大小,
SUBSTRING (str , position [,length ]) //從str的position開始,取length個字符,
注：mysql中處理字符串時，默認第一個字符下標(biāo)為1，即參數(shù)position必須大于等于1
mysql> select substring('abcd',0,2);
+-----------------------+
| substring('abcd',0,2) |
+-----------------------+
| |
+-----------------------+
1 row in set (0.00 sec)
mysql> select substring('abcd',1,2);
+-----------------------+
| substring('abcd',1,2) |
+-----------------------+
| ab |
+-----------------------+
1 row in set (0.02 sec)
TRIM([[BOTH|LEADING|TRAILING] [padding] FROM]string2) //去除指定位置的指定字符
UCASE (string2 ) //轉(zhuǎn)換成大寫
RIGHT(string2,length) //取string2最后length個字符
SPACE(count) //生成count個空格
ABS (number2 ) //絕對值
BIN (decimal_number ) //十進制轉(zhuǎn)二進制
CEILING (number2 ) //向上取整
CONV(number2,from_base,to_base) //進制轉(zhuǎn)換
FLOOR (number2 ) //向下取整
FORMAT (number,decimal_places ) //保留小數(shù)位數(shù)
HEX (DecimalNumber ) //轉(zhuǎn)十六進制
注：HEX()中可傳入字符串，則返回其ASC-11碼，如HEX('DEF')返回4142143
也可以傳入十進制整數(shù)，返回其十六進制編碼，如HEX(25)返回19
LEAST (number , number2 [,..]) //求最小值
MOD (numerator ,denominator ) //求余
POWER (number ,power ) //求指數(shù)
RAND([seed]) //隨機數(shù)
ROUND (number [,decimals ]) //四舍五入,decimals為小數(shù)位數(shù)]
注：返回類型并非均為整數(shù)，如：
(1)默認變?yōu)檎沃?br />mysql> select round(1.23);
+-------------+
| round(1.23) |
+-------------+
| 1 |
+-------------+
1 row in set (0.00 sec)
mysql> select round(1.56);
+-------------+
| round(1.56) |
+-------------+
| 2 |
+-------------+
1 row in set (0.00 sec)
(2)可以設(shè)定小數(shù)位數(shù)，返回浮點型數(shù)據(jù)
mysql> select round(1.567,2);
+----------------+
| round(1.567,2) |
+----------------+
| 1.57 |
+----------------+
1 row in set (0.00 sec)
SIGN (number2 ) //返回符號,正負或0
SQRT(number2) //開平方
