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[数据库]MySQL 正则表达式


介绍

正则表达式用来描述或者匹配符合规则的字符串。它的用法和like比较相似,但是它又比like更强大,能够实现一些很特殊的规则匹配;正则表达式需要使用REGEXP命令,匹配上返回"1"匹配不上返回"0",REGEXP相当于like '%%'。

 

 

命令

说明

^

在字符的开启处进行匹配

$

在字符的末尾处进行匹配

.

匹配任何字符(包括回车和新行)

[….]

匹配括号内的任意单个字符

[m-n]

匹配m到n之间的任意单个字符,例如[0-9],[a-z],[A-Z]

[^..]

不能匹配括号内的任意单个字符

a*

匹配0个或多个a,包括空

a+

匹配一个或多个a,不包括空

a?

匹配一个或0个a

a1| a2

匹配a1或a2

a{m}

匹配m个a

a{m,}

匹配m个或者更多个a

a{m,n}

匹配m到n个a

a{,n}

匹配0到n个a

(….)

将模式元素组成单一元素,例如(do)*意思是匹配0个多或多个do

 

 ^

在字符串开始处进行匹配

mysql> SELECT 'abc' REGEXP '^a';+-------------------+| 'abc' REGEXP '^a' |+-------------------+|         1 |+-------------------+1 row in set (0.00 sec)

$

在字符串末尾开始匹配

mysql> SELECT 'abc' REGEXP 'a$';+-------------------+| 'abc' REGEXP 'a$' |+-------------------+|         0 |+-------------------+1 row in set (0.01 sec)mysql> SELECT 'abc' REGEXP 'c$';+-------------------+| 'abc' REGEXP 'c$' |+-------------------+|         1 |+-------------------+1 row in set (0.00 sec)

.

匹配任意字符

mysql> SELECT 'abc' REGEXP '.a';+-------------------+| 'abc' REGEXP '.a' |+-------------------+|         0 |+-------------------+1 row in set (0.00 sec)mysql> SELECT 'abc' REGEXP '.b';+-------------------+| 'abc' REGEXP '.b' |+-------------------+|         1 |+-------------------+1 row in set (0.00 sec)mysql> SELECT 'abc' REGEXP '.c';+-------------------+| 'abc' REGEXP '.c' |+-------------------+|         1 |+-------------------+1 row in set (0.00 sec)mysql> SELECT 'abc' REGEXP 'a.';+-------------------+| 'abc' REGEXP 'a.' |+-------------------+|         1 |+-------------------+1 row in set (0.00 sec)

[...]

匹配括号内的任意单个字符

mysql> SELECT 'abc' REGEXP '[xyz]';+----------------------+| 'abc' REGEXP '[xyz]' |+----------------------+|          0 |+----------------------+1 row in set (0.00 sec)mysql> SELECT 'abc' REGEXP '[xaz]';+----------------------+| 'abc' REGEXP '[xaz]' |+----------------------+|          1 |+----------------------+1 row in set (0.00 sec)

[^...]:注意^符合只有在[]内才是取反的意思,在别的地方都是表示开始处匹配

 匹配不出括号没的任意个字符,注意:REGEXP 前的匹配字符作为一个整体

mysql> SELECT 'a' REGEXP '[^abc]';+---------------------+| 'a' REGEXP '[^abc]' |+---------------------+|          0 |+---------------------+1 row in set (0.00 sec)mysql> SELECT 'x' REGEXP '[^abc]';+---------------------+| 'x' REGEXP '[^abc]' |+---------------------+|          1 |+---------------------+1 row in set (0.00 sec)

mysql> SELECT 'abc' REGEXP '[^a]';+---------------------+| 'abc' REGEXP '[^a]' |+---------------------+|          1 |+---------------------+1 row in set (0.00 sec)

'abc'作为一个整体,所以它匹配不了a

a*

匹配0个或多个a,包括空字符串。

mysql> SELECT 'stab' REGEXP '.ta*b';
+-----------------------+
| 'stab' REGEXP '.ta*b' |
+-----------------------+
| 1 |
+-----------------------+
1 row in set (0.00 sec)

mysql> SELECT 'stb' REGEXP '.ta*b';
+----------------------+
| 'stb' REGEXP '.ta*b' |
+----------------------+
| 1 |
+----------------------+
1 row in set (0.00 sec)


mysql> SELECT '' REGEXP 'a*';+----------------+| '' REGEXP 'a*' |+----------------+|       1 |+----------------+1 row in set (0.00 sec)

a+

匹配1个或者多个a,但是不包括空字符

mysql> SELECT 'stab' REGEXP '.ta+b';+-----------------------+| 'stab' REGEXP '.ta+b' |+-----------------------+|           1 |+-----------------------+1 row in set (0.00 sec)mysql> SELECT 'stb' REGEXP '.ta+b';+----------------------+| 'stb' REGEXP '.ta+b' |+----------------------+|          0 |+----------------------+1 row in set (0.00 sec)

a?

匹配0个或者1个a

mysql> SELECT 'stb' REGEXP '.ta?b';+----------------------+| 'stb' REGEXP '.ta?b' |+----------------------+|          1 |+----------------------+1 row in set (0.00 sec)mysql> SELECT 'stab' REGEXP '.ta?b';+-----------------------+| 'stab' REGEXP '.ta?b' |+-----------------------+|           1 |+-----------------------+1 row in set (0.00 sec)mysql> SELECT 'staab' REGEXP '.ta?b';+------------------------+| 'staab' REGEXP '.ta?b' |+------------------------+|           0 |+------------------------+1 row in set (0.00 sec)

a1|a2

匹配a1或者a2,

mysql> SELECT 'a' REGEXP 'a|b';+------------------+| 'a' REGEXP 'a|b' |+------------------+|        1 |+------------------+1 row in set (0.00 sec)mysql> SELECT 'b' REGEXP 'a|b';+------------------+| 'b' REGEXP 'a|b' |+------------------+|        1 |+------------------+1 row in set (0.00 sec)mysql> SELECT 'b' REGEXP '^(a|b)';+---------------------+| 'b' REGEXP '^(a|b)' |+---------------------+|          1 |+---------------------+1 row in set (0.00 sec)mysql> SELECT 'a' REGEXP '^(a|b)';+---------------------+| 'a' REGEXP '^(a|b)' |+---------------------+|          1 |+---------------------+1 row in set (0.00 sec)mysql> SELECT 'c' REGEXP '^(a|b)';+---------------------+| 'c' REGEXP '^(a|b)' |+---------------------+|          0 |+---------------------+1 row in set (0.00 sec)

注意:^符合只有在[]内才是取反的意思,在别的地方都是表示开始处匹配

a{m}

匹配m个a

mysql> SELECT 'auuuuc' REGEXP 'au{4}c';+--------------------------+| 'auuuuc' REGEXP 'au{4}c' |+--------------------------+|            1 |+--------------------------+1 row in set (0.00 sec)mysql> SELECT 'auuuuc' REGEXP 'au{3}c';+--------------------------+| 'auuuuc' REGEXP 'au{3}c' |+--------------------------+|            0 |+--------------------------+1 row in set (0.00 sec)

a{m,}

匹配m个或者更多个a

mysql> SELECT 'auuuuc' REGEXP 'au{3,}c';+---------------------------+| 'auuuuc' REGEXP 'au{3,}c' |+---------------------------+|             1 |+---------------------------+1 row in set (0.00 sec)mysql> SELECT 'auuuuc' REGEXP 'au{4,}c';+---------------------------+| 'auuuuc' REGEXP 'au{4,}c' |+---------------------------+|             1 |+---------------------------+1 row in set (0.00 sec)mysql> SELECT 'auuuuc' REGEXP 'au{5,}c';+---------------------------+| 'auuuuc' REGEXP 'au{5,}c' |+---------------------------+|             0 |+---------------------------+1 row in set (0.00 sec)

a{m,n}

匹配m到n个a,包含m和n

mysql> SELECT 'auuuuc' REGEXP 'au{3,5}c';+----------------------------+| 'auuuuc' REGEXP 'au{3,5}c' |+----------------------------+|             1 |+----------------------------+1 row in set (0.00 sec)mysql> SELECT 'auuuuc' REGEXP 'au{4,5}c';+----------------------------+| 'auuuuc' REGEXP 'au{4,5}c' |+----------------------------+|             1 |+----------------------------+1 row in set (0.00 sec)mysql> SELECT 'auuuuc' REGEXP 'au{5,10}c';+-----------------------------+| 'auuuuc' REGEXP 'au{5,10}c' |+-----------------------------+|              0 |+-----------------------------+1 row in set (0.00 sec)

a{,n}

这个暂时还没有测出来,意思应该不是匹配0到n个a,如果是表达0到n个a也可以用{0,n}代替

 

(abc)

将abc作为一个序列匹配,不用括号括起来都是用单个字符去匹配,如果要把多个字符作为一个整体去匹配就需要用到括号,所以括号适合上面的所有情况。

mysql> SELECT 'xababy' REGEXP 'x(abab)y';+----------------------------+| 'xababy' REGEXP 'x(abab)y' |+----------------------------+|             1 |+----------------------------+1 row in set (0.00 sec)mysql> SELECT 'xababy' REGEXP 'x(ab)*y';+---------------------------+| 'xababy' REGEXP 'x(ab)*y' |+---------------------------+|             1 |+---------------------------+1 row in set (0.00 sec)mysql> SELECT 'xababy' REGEXP 'x(ab){1,2}y';+-------------------------------+| 'xababy' REGEXP 'x(ab){1,2}y' |+-------------------------------+|               1 |+-------------------------------+1 row in set (0.00 sec)

 

总结

 特别要注意最后的()的命令,如果不使用()那么所有的都是指单个字符去做匹配,如果需要使用多个字符作为一个整体去匹配就需要将多个字符使用()给括起来

 

 


备注:

    作者:pursuer.chen

    博客:http://www.cnblogs.com/chenmh

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