Regular expressions do not match NULL values. This is true both for REGEXP and for NOT REGEXP

      
mysql>
mysql>
mysql> SELECT NULL REGEXP '.*', NULL NOT REGEXP '.*';
+------------------+----------------------+
| NULL REGEXP '.*' | NULL NOT REGEXP '.*' |
+------------------+----------------------+
|             NULL |                 NULL |
+------------------+----------------------+
1 row in set (0.00 sec)

mysql>

1.	REGEXP 'e'
2.	REGEXP '^ba'
3.	REGEXP and CONCAT
4.	REGEXP '[abc]'
5.	REGEXP 'm.n'
6.	REGEXP '[men][men]'
7.	POSTCODE REGEXP '[0-9][0-9][a-z][a-z]'
8.	NAME REGEXP '^[a-z]{7}'
9.	NAME REGEXP '^[a-z]{6,7}$'
10.	POSTCODE REGEXP '4{4}'
11.	REGEXP '[[.space.]]'
12.	REGEXP '[[:<:]]Street[[:>:]]'
13.	NAME REGEXP '^n.*e$'
14.	REGEXP '[a-z]{9}'
15.	SELECT c, c REGEXP '.', c REGEXP '^', c REGEXP '$' FROM mytable;
16.	With REGEXP, you need a double backslash to match a metacharacter literally:
17.	The primary options that you can use with the REGEXP operator to create expressions in your SQL statements.
18.	Be more specific with the REGEXP operator by extending the specified value used by the operator
19.	Pattern Matching with REGEXP
20.	The command REGEXP offers many more possibilities for formulating a pattern,

Regular expressions do not match NULL values. This is true both for REGEXP and for NOT REGEXP : REGEXP « Regular Expression « SQL / MySQL

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