MYSQL - 模式匹配
MySQL提供标准的SQL模式匹配，可以使用"_"匹配单个字符，%匹配任意数量的字符(包括0个字符)。当使用模式匹配时，用LIKE和NOT LIKE比较操作取代=和<>操作。
查询以"b"开头的名字的宠物
mysql> select * from pet where name like 'b%'; +--------+--------+---------+------+------------+------------+ | name | owner | species | sex | birth | death | +--------+--------+---------+------+------------+------------+ | Buffy | Harold | dog | f | 1989-05-13 | NULL | | Bowser | Diane | dog | m | 1979-08-31 | 1995-07-29 | +--------+--------+---------+------+------------+------------+ 2 rows in set (0.00 sec) mysql>
查询以fy结尾的名字的宠物
mysql> select * from pet where name like '%fy'; +--------+--------+---------+------+------------+-------+ | name | owner | species | sex | birth | death | +--------+--------+---------+------+------------+-------+ | Fluffy | Harold | cat | f | 1993-02-04 | NULL | | Buffy | Harold | dog | f | 1989-05-13 | NULL | +--------+--------+---------+------+------------+-------+ 2 rows in set (0.00 sec) mysql>
查询名字中包含'w'的宠物
mysql> select * from pet where name like '%w%'; +----------+-------+---------+------+------------+------------+ | name | owner | species | sex | birth | death | +----------+-------+---------+------+------------+------------+ | Whistler | Gwen | bird | NULL | 0000-00-00 | NULL | | Claws | Gwen | cat | m | 1994-03-17 | NULL | | Bowser | Diane | dog | m | 1979-08-31 | 1995-07-29 | +----------+-------+---------+------+------------+------------+ 3 rows in set (0.01 sec) mysql>
查询名字中精确包含5个字符的宠物，使用5个'_'匹配5个字符
mysql> select * from pet where name like '_____'; +-------+--------+---------+------+------------+-------+ | name | owner | species | sex | birth | death | +-------+--------+---------+------+------------+-------+ | Claws | Gwen | cat | m | 1994-03-17 | NULL | | Buffy | Harold | dog | f | 1989-05-13 | NULL | +-------+--------+---------+------+------------+-------+ 2 rows in set (0.00 sec) mysql>
MySQL提供的另一种类型的模式匹配用的是扩展的正则表达式。当使用这种类型的模式匹配时，用REGEXP和NOT REGEXP操作(或RLIKE和NOT RLIKE)
下面列表描述了扩展的正则表达式的一些使用
- "."匹配任意的单个字符
- "[...]"匹配在括号中的任意字符。如[abc]匹配“a", "b" 或"c"。匹配一个范围的字符，用一个连字符"-"，[a-z]匹配任意字母，而[0-9]匹配任意数字。
- "*"匹配0或多个其之前的实例。如"x*"匹配任意数量的"x"字符，"[0-9]*"匹配任意数量的数字，而".*"匹配任意数量的字符。
- 如果被测值的任意位置能与模式匹配，则REGEXP模式匹配成功（LIKE类型的模式匹配则要求整个被测值都匹配模式成功）
- 为使一个模式从开头或结尾匹配，使用"^"在模式开头或使用"$"在模式结尾。
使用REGEXP重写之前的查询语句
查询以"b"开头的名字的宠物
mysql> select * from pet where name rlike '^b'; +--------+--------+---------+------+------------+------------+ | name | owner | species | sex | birth | death | +--------+--------+---------+------+------------+------------+ | Buffy | Harold | dog | f | 1989-05-13 | NULL | | Bowser | Diane | dog | m | 1979-08-31 | 1995-07-29 | +--------+--------+---------+------+------------+------------+ 2 rows in set (0.00 sec) mysql> select * from pet where name regexp '^b'; +--------+--------+---------+------+------------+------------+ | name | owner | species | sex | birth | death | +--------+--------+---------+------+------------+------------+ | Buffy | Harold | dog | f | 1989-05-13 | NULL | | Bowser | Diane | dog | m | 1979-08-31 | 1995-07-29 | +--------+--------+---------+------+------------+------------+ 2 rows in set (0.00 sec) mysql>
查询以fy结尾的名字的宠物
mysql> select * from pet where name rlike 'fy$'; +--------+--------+---------+------+------------+-------+ | name | owner | species | sex | birth | death | +--------+--------+---------+------+------------+-------+ | Fluffy | Harold | cat | f | 1993-02-04 | NULL | | Buffy | Harold | dog | f | 1989-05-13 | NULL | +--------+--------+---------+------+------------+-------+ 2 rows in set (0.00 sec) mysql> select * from pet where name regexp 'fy$'; +--------+--------+---------+------+------------+-------+ | name | owner | species | sex | birth | death | +--------+--------+---------+------+------------+-------+ | Fluffy | Harold | cat | f | 1993-02-04 | NULL | | Buffy | Harold | dog | f | 1989-05-13 | NULL | +--------+--------+---------+------+------------+-------+ 2 rows in set (0.00 sec) mysql>
如果希望REGEXP比较是大小写敏感的，使用BINARY关键字。以下查询仅匹配小写字母"b"在名字的开头。
mysql> select * from pet where name rlike binary '^b'; Empty set (0.00 sec) mysql> select * from pet where name regexp binary '^b'; Empty set (0.00 sec) mysql>
查询名字中包含'w'的宠物
mysql> select * from pet where name rlike 'w'; +----------+-------+---------+------+------------+------------+ | name | owner | species | sex | birth | death | +----------+-------+---------+------+------------+------------+ | Whistler | Gwen | bird | NULL | 0000-00-00 | NULL | | Claws | Gwen | cat | m | 1994-03-17 | NULL | | Bowser | Diane | dog | m | 1979-08-31 | 1995-07-29 | +----------+-------+---------+------+------------+------------+ 3 rows in set (0.00 sec) mysql> select * from pet where name regexp 'w'; +----------+-------+---------+------+------------+------------+ | name | owner | species | sex | birth | death | +----------+-------+---------+------+------------+------------+ | Whistler | Gwen | bird | NULL | 0000-00-00 | NULL | | Claws | Gwen | cat | m | 1994-03-17 | NULL | | Bowser | Diane | dog | m | 1979-08-31 | 1995-07-29 | +----------+-------+---------+------+------------+------------+ 3 rows in set (0.00 sec) mysql>
查询名字中精确包含5个字符的宠物
mysql> select * from pet where name rlike '^.....$'; +-------+--------+---------+------+------------+-------+ | name | owner | species | sex | birth | death | +-------+--------+---------+------+------------+-------+ | Claws | Gwen | cat | m | 1994-03-17 | NULL | | Buffy | Harold | dog | f | 1989-05-13 | NULL | +-------+--------+---------+------+------------+-------+ 2 rows in set (0.00 sec) mysql> select * from pet where name regexp '^.....$'; +-------+--------+---------+------+------------+-------+ | name | owner | species | sex | birth | death | +-------+--------+---------+------+------------+-------+ | Claws | Gwen | cat | m | 1994-03-17 | NULL | | Buffy | Harold | dog | f | 1989-05-13 | NULL | +-------+--------+---------+------+------------+-------+ 2 rows in set (0.00 sec) mysql>
也可以使用{n}（重复n次）操作
mysql> select * from pet where name rlike '^.{5}$';
+-------+--------+---------+------+------------+-------+
| name | owner | species | sex | birth | death |
+-------+--------+---------+------+------------+-------+
| Claws | Gwen | cat | m | 1994-03-17 | NULL |
| Buffy | Harold | dog | f | 1989-05-13 | NULL |
+-------+--------+---------+------+------------+-------+
2 rows in set (0.00 sec)
mysql> select * from pet where name regexp '^.{5}$';
+-------+--------+---------+------+------------+-------+
| name | owner | species | sex | birth | death |
+-------+--------+---------+------+------------+-------+
| Claws | Gwen | cat | m | 1994-03-17 | NULL |
| Buffy | Harold | dog | f | 1989-05-13 | NULL |
+-------+--------+---------+------+------------+-------+
2 rows in set (0.00 sec)
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