mysql常用字符串操作函数大全,以及实例
测试表 CREATE TABLE `string_test` ( `id` int(11) NOT NULL auto_increment COMMENT '用户ID', `name` varchar(50) NOT NULL default '' COMMENT '名称', `job` varchar(23) NOT NULL COMMENT '工作', `sex` tinyint(1) NOT NULL default '1' COMMENT '性别', `hobby` varchar(100) character set utf8 collate utf8_unicode_ci default NULL COMMENT '爱好', PRIMARY KEY (`id`) ) ENGINE=MyISAM DEFAULT CHARSET=utf8 AUTO_INCREMENT=1 ; 测试数据 INSERT INTO `string_test` (`id`, `name`, `job`, `sex`, `hobby`) VALUES (1, 'tank', '农民工', 1, '军棋,游戏,fishing'), (2, 'zhang', 'DUCK', 0, 'fly,make firend'), (3, 'ying', 'no job', 1, 'flying,driving,testing'), (4, 'tankzhang', 'love your love', 1, 'i love you');
mysql字符串操作函数
1,UPPER和UCASE
返回字符串str,根据当前字符集映射(缺省是ISO-8859-1 Latin1)把所有的字符改变成大写。该函数对多字节是可靠的。
mysql> select name,UPPER(name) from string_test where name='tank';
+------+-------------+
| name | UPPER(name) |
+------+-------------+
| tank | TANK |
+------+-------------+
1 row in set (0.00 sec)
2,LOWER和LCASE
返回字符串str,根据当前字符集映射(缺省是ISO-8859-1 Latin1)把所有的字符改变成小写。该函数对多字节是可靠的。
mysql> select sex,LCASE(job) from string_test where job='DUCK';
+------+------------+
| sex | LCASE(job) |
+------+------------+
| 1 | duck |
+------+------------+
1 row in set (0.00 sec)
3,FIND_IN_SET(str,strlist)
如果字符串str在由N子串组成的表strlist之中,返回一个1到N的值。一个字符串表是被“,”分隔的子串组成的一个字符串。如果第一个参数是一个常数字符串并且第二个参数是一种类型为SET的列,FIND_IN_SET()函数被优化而使用位运算!如果str不是在strlist里面或如果 strlist是空字符串,返回0。如果任何一个参数是NULL,返回NULL。如果第一个参数包含一个“,”,该函数将工作不正常。看面是二种不同的效果,可以看一下
mysql> SELECT id,name FROM string_test WHERE find_in_set('fly',hobby);
+----+-------+
| id | name |
+----+-------+
| 2 | zhang |
+----+-------+
1 row in set (0.00 sec)
mysql> SELECT id,name FROM string_test WHERE hobby like 'fly%';
+----+-------+
| id | name |
+----+-------+
| 2 | zhang |
| 3 | ying |
+----+-------+
2 rows in set (0.00 sec)
4,FIELD(str,str1,str2,str3,…)
返回str在str1, str2, str3, …清单的索引。如果str没找到,返回0。FIELD()是ELT()反运算。
mysql> SELECT id, name, FIELD( id, name, sex, job, hobby )
-> FROM string_test where id < 4;
+----+-------+------------------------------------+
| id | name | FIELD( id, name, sex, job, hobby ) |
+----+-------+------------------------------------+
| 1 | tank | 2 |
| 2 | zhang | 0 |
| 3 | ying | 0 |
+----+-------+------------------------------------+
3 rows in set (0.00 sec)
5.ELT(N,str1,str2,str3,…)
如果N= 1,返回str1,如果N= 2,返回str2,等等。如果N小于1或大于参数个数,返回NULL。ELT()是FIELD()反运算。
mysql> SELECT id, name, ELT(1, id, name, sex, job, hobby ) FROM string_test where id < 4;
+----+-------+------------------------------------+
| id | name | ELT(1, id, name, sex, job, hobby ) |
+----+-------+------------------------------------+
| 1 | tank | 1 |
| 2 | zhang | 2 |
| 3 | ying | 3 |
+----+-------+------------------------------------+
3 rows in set (0.00 sec)
mysql> SELECT id, name, ELT(2, id, name, sex, job, hobby ) FROM string_test where id < 4;
+----+-------+------------------------------------+
| id | name | ELT(2, id, name, sex, job, hobby ) |
+----+-------+------------------------------------+
| 1 | tank | tank |
| 2 | zhang | zhang |
| 3 | ying | ying |
+----+-------+------------------------------------+
3 rows in set (0.00 sec)
6,REPLACE(str,from_str,to_str)
返回字符串str,其字符串from_str的所有出现由字符串to_str代替。
mysql> SELECT id,REPLACE(hobby,"firend",'living') FROM string_test WHERE id = 2;
+----+----------------------------------+
| id | REPLACE(hobby,"firend",'living') |
+----+----------------------------------+
| 2 | fly,make living |
+----+----------------------------------+
1 row in set (0.00 sec)
7,REPEAT(str,count)
返回由重复countTimes次的字符串str组成的一个字符串。如果count <= 0,返回一个空字符串。如果str或count是NULL,返回NULL。
mysql> SELECT id,REPEAT(name,2) FROM string_test WHERE id > 1 and id < 4;
+----+----------------+
| id | REPEAT(name,2) |
+----+----------------+
| 2 | zhangzhang |
| 3 | yingying |
+----+----------------+
2 rows in set (0.00 sec)
8,REVERSE(str)
返回颠倒字符顺序的字符串str。
mysql> SELECT id,reverse(name) FROM string_test WHERE id > 1 and id < 4;
+----+---------------+
| id | reverse(name) |
+----+---------------+
| 2 | gnahz |
| 3 | gniy |
+----+---------------+
2 rows in set (0.00 sec)
9,INSERT(str,pos,len,newstr)
返回字符串str,在位置pos起始的子串且len个字符长得子串由字符串newstr代替。
mysql> select id,name,INSERT(hobby,10,6,'living') from string_test where id = 2;
+----+-------+-----------------------------+
| id | name | INSERT(hobby,10,6,'living') |
+----+-------+-----------------------------+
| 2 | zhang | fly,make living |
+----+-------+-----------------------------+
1 row in set (0.00 sec)
10,SUBSTRING(str FROM pos)
从字符串str的起始位置pos返回一个子串。下面的sub2没有值,因为mysql数据库的下标是从1开始的。
mysql> SELECT id, substring( hobby, 1, 6) AS sub1, substring( hobby from 0 for 8
) AS sub2,substring( hobby,2) AS sub3, substring( hobby from 4 ) AS sub4 FROM s
tring_test WHERE id =4;
+----+--------+------+-----------+---------+
| id | sub1 | sub2 | sub3 | sub4 |
+----+--------+------+-----------+---------+
| 4 | i love | | love you | ove you |
+----+--------+------+-----------+---------+
1 row in set (0.00 sec)
11,SUBSTRING_INDEX(str,delim,count)
返回从字符串str的第count个出现的分隔符delim之后的子串。如果count是正数,返回最后的分隔符到左边(从左边数) 的所有字符。如果count是负数,返回最后的分隔符到右边的所有字符(从右边数)。
mysql> SELECT id,SUBSTRING_INDEX(hobby,',',2) as test1,SUBSTRING_INDEX(hobby,','
,-1) as test2 FROM string_test WHERE id = 3;
+----+----------------+---------+
| id | test1 | test2 |
+----+----------------+---------+
| 3 | flying,driving | testing |
+----+----------------+---------+
1 row in set (0.01 sec)
12,LTRIM(str)
返回删除了其前置空格字符的字符串str。
mysql> SELECT id,LTRIM(job) FROM string_test WHERE id = 4;
+----+----------------+
| id | LTRIM(job) |
+----+----------------+
| 4 | love your love |
+----+----------------+
1 row in set (0.00 sec)
13,RTRIM(str)
返回删除了其拖后空格字符的字符串str。
mysql> SELECT id,RTRIM(job) FROM string_test WHERE id = 4;
+----+----------------+
| id | RTRIM(job) |
+----+----------------+
| 4 | love your love |
+----+----------------+
1 row in set (0.00 sec)
14,TRIM([[BOTH | LEADING | TRAILING] [remstr] FROM] str)
返回字符串str,其所有remstr前缀或后缀被删除了。如果没有修饰符BOTH、LEADING或TRAILING给出,BOTH被假定。如果remstr没被指定,空格被删除。
mysql> select trim(' test ');
+-----------------+
| trim(' test ') |
+-----------------+
| test |
+-----------------+
1 row in set (0.01 sec)
mysql> SELECT id,TRIM(LEADING "love" from job) as test1,TRIM(BOTH "love" from jo
b) as test2,TRIM(TRAILING "love" from job) as test3 FROM string_test WHERE id =
4
-> ;
+----+------------+--------+------------+
| id | test1 | test2 | test3 |
+----+------------+--------+------------+
| 4 | your love | your | love your |
+----+------------+--------+------------+
1 row in set (0.00 sec)
15,MID(str,pos,len)
从字符串str返回一个len个字符的子串,从位置pos开始。使用FROM的变种形式是ANSI SQL92语法。
mysql> SELECT id, mid( hobby, 1, 6 ) AS sub1, mid( hobby
-> FROM 0
-> FOR 8 ) AS sub2, mid( hobby, 2 ) AS sub3, mid( hobby
-> FROM 4 ) AS sub4
-> FROM string_test
-> WHERE id =4 ;
+----+--------+------+-----------+---------+
| id | sub1 | sub2 | sub3 | sub4 |
+----+--------+------+-----------+---------+
| 4 | i love | | love you | ove you |
+----+--------+------+-----------+---------+
1 row in set (0.00 sec)
mysql>
16,LPAD(str,len,padstr)
返回字符串str,左面用字符串padstr填补直到str是len个字符长。
mysql> SELECT id,LPAD(name,11,"zhang ") FROM string_test WHERE id = 3;
+----+------------------------+
| id | LPAD(name,11,"zhang ") |
+----+------------------------+
| 3 | zhang zying |
+----+------------------------+
1 row in set (0.00 sec)
17,RPAD(str,len,padstr)
返回字符串str,右面用字符串padstr填补直到str是len个字符长。
mysql> SELECT id,RPAD(name,11," ying") FROM string_test WHERE id = 2;
+----+-----------------------+
| id | RPAD(name,11," ying") |
+----+-----------------------+
| 2 | zhang ying |
+----+-----------------------+
1 row in set (0.00 sec)
18,LEFT(str,len)
返回字符串str的最左面len个字符。
mysql> SELECT id,left(job,4) FROM string_test WHERE id = 4;
+----+-------------+
| id | left(job,4) |
+----+-------------+
| 4 | love |
+----+-------------+
1 row in set (0.00 sec)
19,RIGHT(str,len)
返回字符串str的最右面len个字符。
mysql> SELECT id,right(job,4) FROM string_test WHERE id = 4;
+----+--------------+
| id | right(job,4) |
+----+--------------+
| 4 | love |
+----+--------------+
1 row in set (0.00 sec)
20,位置控制函数
POSITION(substr IN str)
返回子串substr在字符串str第一个出现的位置,如果substr不是在str里面,返回0.
LOCATE(substr,str,pos)
返回子串substr在字符串str第一个出现的位置,从位置pos开始。如果substr不是在str里面,返回0。
INSTR(str,substr)
返回子串substr在字符串str中的第一个出现的位置。这与有2个参数形式的LOCATE()相同,除了参数被颠倒。
mysql> SELECT id,INSTR(job,"you") as instr,LOCATE('love',job,3) as locate,POSITI
ON('love' in job) as position FROM string_test WHERE id = 4;
+----+-------+--------+----------+
| id | instr | locate | position |
+----+-------+--------+----------+
| 4 | 6 | 11 | 1 |
+----+-------+--------+----------+
1 row in set (0.00 sec)
21,得到字符串长度的函数
LENGTH(str),OCTET_LENGTH(str),CHAR_LENGTH(str),CHARACTER_LENGTH(str)
mysql> SELECT id,LENGTH(job) as one,OCTET_LENGTH(job) as two,CHAR_LENGTH(job) as
three,CHARACTER_LENGTH(job) as four FROM string_test WHERE id = 4;
+----+-----+-----+-------+------+
| id | one | two | three | four |
+----+-----+-----+-------+------+
| 4 | 14 | 14 | 14 | 14 |
+----+-----+-----+-------+------+
1 row in set (0.00 sec)
23,合并多个字符串,或者表中的多个字段
CONCAT(str1,str2,…) // 不设置分隔符
select concat('001','-','小明','-','85') as result; // 设置分隔符
返回来自于参数连结的字符串。如果任何参数是NULL,返回NULL。可以有超过2个的参数。一个数字参数被变换为等价的字符串形式。
mysql> SELECT id,CONCAT(name,job,hobby) FROM string_test WHERE id = 4;
+----+-----------------------------------+
| id | CONCAT(name,job,hobby) |
+----+-----------------------------------+
| 4 | tankzhanglove your lovei love you |
+----+-----------------------------------+
1 row in set (0.00 sec)
concat_ws()
功能:和concat()一样,将多个字符串连接成一个字符串,但是可以一次性指定分隔符(concat_ws就是concat with separator)
语法:concat_ws(separator, str1, str2, ...)
说明:第一个参数指定分隔符,不可省略。需要注意的是分隔符不能为null,如果为null,则返回结果为null。
用法:
(1)设置 '-' 作为分隔符
mysql> select concat_ws('-','001','小明','85') as result;
+---------------+
| result |
+---------------+
| 001-小明-85 |
+---------------+
假如每个学生都有几个科目(subject 01/02)的成绩,这样同一个学号(id:001)、同一名字(name:小明)会出现多次,只是最后一个字段分数不同(score:85/90)。如何让每个学号、名字都只出现一次呢?
接下来介绍group_concat(),结合group by使用。
3. group_concat()
功能:将group by产生的同一个分组中的值连接起来,返回一个字符串结果。
语法:group_concat( [distinct] 要连接的字段 [order by 排序字段 asc/desc ] [separator '分隔符'] )
说明:通过使用distinct可以排除重复值;如果希望对结果中的值进行排序,可以使用order by子句;separator是一个字符串值,缺省为一个逗号。
用法:
select concat_ws('-',id,name,group_concat(score order by subject separator'-')) as result
from grade
group by name;
result:
001-小明-85-90
23,进制转换
BIN(N)
返回二进制值N的一个字符串表示,在此N是一个长整数(BIGINT)数字,这等价于CONV(N,10,2)。如果N是NULL,返回NULL。
OCT(N)
返回八进制值N的一个字符串的表示,在此N是一个长整型数字,这等价于CONV(N,10,8)。如果N是NULL,返回NULL。
HEX(N)
返回十六进制值N一个字符串的表示,在此N是一个长整型(BIGINT)数字,这等价于CONV(N,10,16)。如果N是NULL,返回NULL。
ASCII(str)
返回字符串str的最左面字符的ASCII代码值。如果str是空字符串,返回0。如果str是NULL,返回NULL。
mysql> select bin(20),oct(20),hex(20),ascii(20);
+---------+---------+---------+-----------+
| bin(20) | oct(20) | hex(20) | ascii(20) |
+---------+---------+---------+-----------+
| 10100 | 24 | 14 | 50 |
+---------+---------+---------+-----------+
1 row in set (0.02 sec)
上面我只例举了一部分对字符串进行操作的函数,并且是我觉得我们平时会用的,有可能会用到的一些函数。
posted on 2021-06-07 17:07 UnmatchedSelf 阅读(663) 评论(1) 编辑 收藏 举报