(mysql.info.gz) String syntax

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 9.1.1 Strings
 -------------
 
 A string is a sequence of characters, surrounded by either single quote
 (`'') or double quote (`"') characters.  Examples:
 
      'a string'
      "another string"
 
 If the server SQL mode has `ANSI_QUOTES' enabled, string literals can be
 quoted only with single quotes. A string quoted with double quotes will
 be interpreted as an identifier.
 
 As of MySQL 4.1.1, string literals may have an optional character set
 introducer and `COLLATE' clause:
 
      [_CHARSET_NAME]'STRING' [COLLATE COLLATION_NAME]
 
 Examples:
      SELECT _latin1'STRING';
      SELECT _latin1'STRING' COLLATE latin1_danish_ci;
 
 For more information about these forms of string syntax, see 
 Charset-literal.
 
 Within a string, certain sequences have special meaning.  Each of these
 sequences begins with a backslash (`\'), known as the _escape
 character_.  MySQL recognizes the following escape sequences:
 
 `\0'    An ASCII 0 (`NUL') character.
 `\''    A single quote (`'') character.
 `\"'    A double quote (`"') character.
 `\b'    A backspace character.
 `\n'    A newline (linefeed) character.
 `\r'    A carriage return character.
 `\t'    A tab character.
 `\Z'    ASCII 26 (Control-Z).  This character can be encoded as `\Z' to
         allow you to work around the problem that ASCII 26 stands for
         END-OF-FILE on Windows.  (ASCII 26 will cause problems if you
         try to use `mysql DB_NAME < FILE_NAME'.)
 `\\'    A backslash (`\') character.
 `\%'    A `%' character. See note following table.
 `\_'    A `_' character. See note following table.
 
 These sequences are case sensitive. For example, `\b' is interpreted as
 a backspace, but `\B' is interpreted as `B'.
 
 The `\%' and `\_' sequences are used to search for literal instances of
 `%' and `_' in pattern-matching contexts where they would otherwise be
 interpreted as wildcard characters.  String comparison functions.
 Note that if you use `\%' or `\_' in other contexts, they return the
 strings `\%' and `\_' and not `%' and `_'.
 
 In all other escape sequences, backslash is ignored.  That is, the
 escaped character is interpreted as if it was not escaped.
 
 There are several ways to include quotes within a string:
 
    * A `'' inside a string quoted with `'' may be written as `'''.
 
    * A `"' inside a string quoted with `"' may be written as `""'.
 
    * You can precede the quote character with 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.
 
 The following `SELECT' statements demonstrate how quoting and escaping
 work:
 
      mysql> SELECT 'hello', '"hello"', '""hello""', 'hel''lo', '\'hello';
      +-------+---------+-----------+--------+--------+
      | hello | "hello" | ""hello"" | hel'lo | 'hello |
      +-------+---------+-----------+--------+--------+
 
      mysql> SELECT "hello", "'hello'", "''hello''", "hel""lo", "\"hello";
      +-------+---------+-----------+--------+--------+
      | hello | 'hello' | ''hello'' | hel"lo | "hello |
      +-------+---------+-----------+--------+--------+
 
      mysql> SELECT 'This\nIs\nFour\nLines';
      +--------------------+
      | This
      Is
      Four
      Lines |
      +--------------------+
 
      mysql> SELECT 'disappearing\ backslash';
      +------------------------+
      | disappearing backslash |
      +------------------------+
 
 If you want to insert binary data into a string column (such as a
 `BLOB'), the following characters must be represented by escape
 sequences:
 
 `NUL'   `NUL' byte (ASCII 0).  Represent this character by `\0' (a
         backslash followed by an ASCII `0' character).
 `\'     Backslash (ASCII 92).  Represent this character by `\\'.
 `''     Single quote (ASCII 39).  Represent this character by `\''.
 `"'     Double quote (ASCII 34).  Represent this character by `\"'.
 
 When writing application programs, any string that might contain any of
 these special characters must be properly escaped before the string is
 used as a data value in an SQL statement that is sent to the MySQL
 server.  You can do this in two ways:
 
    * Process the string with a function that escapes the special
      characters.  For example, in a C program, you can use the
      `mysql_real_escape_string()' C API function to escape characters.
       `mysql_real_escape_string()' mysql_real_escape_string.  The
      Perl DBI interface provides a `quote' method to convert special
      characters to the proper escape sequences.   Perl.
 
    * As an alternative to explicitly escaping special characters, many
      MySQL APIs provide a placeholder capability that allows you to
      insert special markers into a query string, and then bind data
      values to them when you issue the query.  In this case, the API
      takes care of escaping special characters in the values for you.
 
 

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