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)
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
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