This section describes how to write literal 
values in MySQL. These include strings, numbers,
 hexadecimal values, boolean values, and NULL. 
The section also covers the various nuances and 
“gotchas� that you may run into when dealing 
with these basic types in MySQL. 
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 is 
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;