A ‘'’ inside a string quoted with ‘'’ may be written as ‘''’.

A ‘"’ inside a string quoted with ‘"’ may be written as ‘""’.

Precede the quote character by an escape character (‘\’).

A ‘'’ inside a string quoted with ‘"’ needs no special treatment and need not be doubled or escaped. In the same way, ‘"’ inside a string quoted with ‘'’ needs no special treatment.

Process the string with a function that escapes the special characters. In a C program, you can use the mysql_real_escape_string() C API function to escape characters. See Section 22.2.3.52, “mysql_real_escape_string()”. The Perl DBI interface provides a quote method to convert special characters to the proper escape sequences. See Section 22.4, “MySQL Perl API”. Other language interfaces may provide a similar capability.

As an alternative to explicitly escaping special characters, many MySQL APIs provide a placeholder capability that enables you to insert special markers into a statement string, and then bind data values to them when you issue the statement. In this case, the API takes care of escaping special characters in the values for you.

expr LIKE pat [ESCAPE 'escape_char']

Pattern matching using SQL simple regular expression comparison. Returns 1 (TRUE) or 0 (FALSE). If either expr or pat is NULL, the result is NULL.

The pattern need not be a literal string. For example, it can be specified as a string expression or table column.

Per the SQL standard, LIKE performs matching on a per-character basis, thus it can produce results different from the = comparison operator:

mysql> SELECT 'ä' LIKE 'ae' COLLATE latin1_german2_ci;
+-----------------------------------------+
| 'ä' LIKE 'ae' COLLATE latin1_german2_ci |
+-----------------------------------------+
|                                       0 |
+-----------------------------------------+
mysql> SELECT 'ä' = 'ae' COLLATE latin1_german2_ci;
+--------------------------------------+
| 'ä' = 'ae' COLLATE latin1_german2_ci |
+--------------------------------------+
|                                    1 |
+--------------------------------------+

With LIKE you can use the following two wildcard characters in the pattern:

mysql> SELECT 'David!' LIKE 'David_';
        -> 1
mysql> SELECT 'David!' LIKE '%D%v%';
        -> 1

To test for literal instances of a wildcard character, precede it by the escape character. If you do not specify the ESCAPE character, ‘\’ is assumed.

mysql> SELECT 'David!' LIKE 'David\_';
        -> 0
mysql> SELECT 'David_' LIKE 'David\_';
        -> 1

To specify a different escape character, use the ESCAPE clause:

mysql> SELECT 'David_' LIKE 'David|_' ESCAPE '|';
        -> 1

The escape sequence should be empty or one character long. As of MySQL 5.1.2, if the NO_BACKSLASH_ESCAPES SQL mode is enabled, the sequence cannot be empty.

The following two statements illustrate that string comparisons are not case sensitive unless one of the operands is a binary string:

mysql> SELECT 'abc' LIKE 'ABC';
        -> 1
mysql> SELECT 'abc' LIKE BINARY 'ABC';
        -> 0

In MySQL, LIKE is allowed on numeric expressions. (This is an extension to the standard SQL LIKE.)

mysql> SELECT 10 LIKE '1%';
        -> 1

Note: Because MySQL uses C escape syntax in strings (for example, ‘\n’ to represent a newline character), you must double any ‘\’ that you use in LIKE strings. For example, to search for ‘\n’, specify it as ‘\\n’. To search for ‘\’, specify it as ‘\\\\’; this is because the backslashes are stripped once by the parser and again when the pattern match is made, leaving a single backslash to be matched against. (Exception: At the end of the pattern string, backslash can be specified as ‘\\’. At the end of the string, backslash stands for itself because there is nothing following to escape.)

expr NOT LIKE pat [ESCAPE 'escape_char']

This is the same as NOT (expr LIKE pat [ESCAPE 'escape_char']).

expr NOT REGEXP pat, expr NOT RLIKE pat

This is the same as NOT (expr REGEXP pat).

expr REGEXP pat expr RLIKE pat

Performs a pattern match of a string expression expr against a pattern pat. The pattern can be an extended regular expression. The syntax for regular expressions is discussed in Appendix G, Regular Expressions. Returns 1 if expr matches pat; otherwise it returns 0. If either expr or pat is NULL, the result is NULL. RLIKE is a synonym for REGEXP, provided for mSQL compatibility.

The pattern need not be a literal string. For example, it can be specified as a string expression or table column.

Note: Because MySQL uses the C escape syntax in strings (for example, ‘\n’ to represent the newline character), you must double any ‘\’ that you use in your REGEXP strings.

REGEXP is not case sensitive, except when used with binary strings.

mysql> SELECT 'Monty!' REGEXP 'm%y%%';
        -> 0
mysql> SELECT 'Monty!' REGEXP '.*';
        -> 1
mysql> SELECT 'new*\n*line' REGEXP 'new\\*.\\*line';
        -> 1
mysql> SELECT 'a' REGEXP 'A', 'a' REGEXP BINARY 'A';
        -> 1  0
mysql> SELECT 'a' REGEXP '^[a-d]';
        -> 1

REGEXP and RLIKE use the current character set when deciding the type of a character. The default is latin1 (cp1252 West European). Warning: These operators are not multi-byte safe.

STRCMP(expr1,expr2)

STRCMP() returns 0 if the strings are the same, -1 if the first argument is smaller than the second according to the current sort order, and 1 otherwise.

mysql> SELECT STRCMP('text', 'text2');
        -> -1
mysql> SELECT STRCMP('text2', 'text');
        -> 1
mysql> SELECT STRCMP('text', 'text');
        -> 0

STRCMP() uses the current character set when performing comparisons. This makes the default comparison behavior case insensitive unless one or both of the operands are binary strings.