mysql字符串函数有哪些？

mysql字符串函数有：

1、LOWER(column|str)：将字符串参数值转换为全小写字母后返回mysql> select lower('SQL Course');+---------------------+| lower('SQL Course') |+---------------------+| sql course|+---------------------+2、UPPER(column|str)：将字符串参数值转换为全大写字母后返回mysql> select upper('Use MYsql');+--------------------+| upper('Use MYsql') |+--------------------+| USE MYSQL|+--------------------+3、CONCAT(column|str1, column|str2,...)：将多个字符串参数首尾相连后返回mysql> select concat('My','S','QL');+-----------------------+| concat('My','S','QL') |+-----------------------+| MySQL|+-----------------------+如果有任何参数为null，则函数返回nullmysql> select concat('My',null,'QL');+------------------------+| concat('My',null,'QL') |+------------------------+| NULL|+------------------------+如果参数是数字，则自动转换为字符串mysql> select concat(14.3,'mysql');+----------------------+| concat(14.3,'mysql') |+----------------------+| 14.3mysql|+----------------------+4、CONCAT_WS(separator,str1,str2,...)：将多个字符串参数以给定的分隔符separator首尾相连后返回mysql> select concat_ws(';','First name','Second name','Last name');+-------------------------------------------------------+| concat_ws(';','First name','Second name','Last name') |+-------------------------------------------------------+| First name;Second name;Last name|+-------------------------------------------------------+！！也就是函数圆括号里的第一个项目用来指定分隔符

5、SUBSTR(str,pos[,len])：从源字符串str中的指定位置pos开始取一个字串并返回

注意：

　　①len指定子串的长度，如果省略则一直取到字符串的末尾；len为负值表示从源字符串的尾部开始取起。

　　②函数SUBSTR()是函数SUBSTRING()的同义词。mysql> select substring('hello world',5);+----------------------------+| substring('hello world',5) |+----------------------------+| o world|+----------------------------+mysql> select substr('hello world',5,3);+---------------------------+| substr('hello world',5,3) |+---------------------------+| o w|+---------------------------+mysql> select substr('hello world',-5);+--------------------------+| substr('hello world',-5) |+--------------------------+| world|+--------------------------+6、LENGTH(str)：返回字符串的存储长度mysql> select length('text'),length('你好');+----------------+------------------+| length('text') | length('你好')|+----------------+------------------+|4 |6 |+----------------+------------------+注意：编码方式不同字符串的存储长度就不一样(‘你好’:utf8是6，gbk是4)

7、CHAR_LENGTH(str)：返回字符串中的字符个数mysql> select char_length('text'),char_length('你好');+---------------------+-----------------------+| char_length('text') | char_length('你好')|+---------------------+-----------------------+|4 |2 |+---------------------+-----------------------+8、INSTR(str, substr)：从源字符串str中返回子串substr第一次出现的位置mysql> select instr('foobarbar','bar');+--------------------------+| instr('foobarbar','bar') |+--------------------------+|4 |+--------------------------+9、LPAD(str, len, padstr)：在源字符串的左边填充给定的字符padstr到指定的长度len，返回填充后的字符串mysql> select lpad('hi',5,'??');+-------------------+| lpad('hi',5,'??') |+-------------------+| ???hi|+-------------------+10、RPAD(str, len, padstr)：在源字符串的右边填充给定的字符padstr到指定的长度len，返回填充后的字符串mysql> select rpad('hi',6,'??');+-------------------+| rpad('hi',6,'??') |+-------------------+| hi????|+-------------------+11、TRIM([{BOTH | LEADING | TRAILING} [remstr] FROM] str), TRIM([remstr FROM] str)：

从源字符串str中去掉两端、前缀或后缀字符remstr并返回；

　　如果不指定remstr，则去掉str两端的空格；不指定BOTH、LEADING、TRAILING ，则默认为 BOTH。mysql> select trim('bar');+-----------------+| trim('bar') |+-----------------+| bar|+-----------------+mysql> select trim(leading 'x' from 'xxxbarxxx');+------------------------------------+| trim(leading 'x' from 'xxxbarxxx') |+------------------------------------+| barxxx|+------------------------------------+mysql> select trim(both 'x' from 'xxxbarxxx');+---------------------------------+| trim(both 'x' from 'xxxbarxxx') |+---------------------------------+| bar|+---------------------------------+mysql> select trim(trailing 'xyz' from 'barxxyz');+-------------------------------------+| trim(trailing 'xyz' from 'barxxyz') |+-------------------------------------+| barx|+-------------------------------------+12、REPLACE(str, from_str, to_str)：在源字符串str中查找所有的子串form_str（大小写敏感），找到后使用替代字符串to_str替换它。返回替换后的字符串mysql> select replace('www.mysql.com','w','Ww');+-----------------------------------+| replace('www.mysql.com','w','Ww') |+-----------------------------------+| WwWwWw.mysql.com|+-----------------------------------+13、LTRIM(str)，RTRIM(str)：去掉字符串的左边或右边的空格(左对齐、右对齐)mysql> SELECTltrim('barbar') rs1, rtrim('barbar') rs2;+-----------+-----------+| rs1| rs2|+-----------+-----------+| barbar|barbar |+-----------+-----------+14、REPEAT(str, count)：将字符串str重复count次后返回mysql> select repeat('MySQL',3);+-------------------+| repeat('MySQL',3) |+-------------------+| MySQLMySQLMySQL|+-------------------+15、REVERSE(str)：将字符串str反转后返回mysql> select reverse('abcdef');+-------------------+| reverse('abcdef') |+-------------------+| fedcba|+-------------------+16、CHAR(N,... [USINGcharset_name])：将每个参数N解释为整数（字符的编码），并返回每个整数对应的字符所构成的字符串(NULL值被忽略)。mysql> select char(77,121,83,81,'76'),char(77,77.3,'77.3');+-------------------------+----------------------+| char(77,121,83,81,'76') | char(77,77.3,'77.3') |+-------------------------+----------------------+| MySQL| MMM|+-------------------------+----------------------+默认情况下，函数返回二进制字符串，若想返回针对特定字符集的字符串，使用using选项mysql> SELECT charset(char(0x65)), charset(char(0x65 USING utf8));+---------------------+--------------------------------+| charset(char(0x65)) | charset(char(0x65 USING utf8)) |+---------------------+--------------------------------+| binary| utf8|+---------------------+--------------------------------+17、FORMAT(X,D[,locale])：以格式‘#,###,###.##’格式化数字X

D指定小数位数

locale指定国家语言(默认的locale为en_US)

mysql> SELECT format(12332.123456, 4),format(12332.2,0);+-------------------------+-------------------+| format(12332.123456, 4) | format(12332.2,0) |+-------------------------+-------------------+| 12,332.1235| 12,332|+-------------------------+-------------------+mysql> SELECT format(12332.2,2,'de_DE');+---------------------------+| format(12332.2,2,'de_DE') |+---------------------------+| 12.332,20|+---------------------------+

18、SPACE(N)：返回由N个空格构成的字符串mysql> select space(3);+----------+| space(3) |+----------+||+----------+19、LEFT(str, len)：返回最左边的len长度的子串mysql> select left('chinaitsoft',5);+-----------------------+| left('chinaitsoft',5) |+-----------------------+| china|+-----------------------+20、RIGHT(str, len)：返回最右边的len长度的子串mysql> select right('chinaitsoft',5);+------------------------+| right('chinaitsoft',5) |+------------------------+| tsoft|+------------------------+21、STRCMP(expr1,expr2)：如果两个字符串是一样的则返回0；如果第一个小于第二个则返回-1；否则返回1mysql> select strcmp('text','text');+-----------------------+| strcmp('text','text') |+-----------------------+|0 |+-----------------------+mysql> SELECT strcmp('text', 'text2'),strcmp('text2', 'text');+-------------------------+-------------------------+| strcmp('text', 'text2') | strcmp('text2', 'text') |+-------------------------+-------------------------+|-1 |1 |+-------------------------+-------------------------+以上就是mysql字符串函数有哪些？的详细内容，更多请关注小潘博客其它相关文章！