The MySQL CONCAT() function concatenates two or more strings by adding them together and returning the concatenated string. It will return a non-binary string if all arguments are non-binary, and a binary string if any argument is binary. Numeric arguments are also converted to their binary string equivalent. The CONCAT() function takes two or more string arguments and returns their concatenated value.

1. MySQL concat() function
Reference :-
http://www.w3resource.com/mysql/string-functions/mysql-concat-function.php
http://dev.mysql.com/doc/refman/5.0/en/string-functions.html#function_concat

2. MySQL concat() function
Description
MySQL CONCAT() function is used to add two
or more strings. It will return non-binary
strings when all the strings are non-binary and
return binary string when any of the specified
string is binary. A numeric argument is also
converted in its equivalent binary string form.
It can be avoided by using an explicit type CAST
Syntax
CONCAT (string1, string2,…)

3. MySQL concat() function
Example of MySQL concat() function
Code:-
SELECT CONCAT('Use',' MySQL');

4. MySQL concat() function
Example of MySQL concat() function on columns
Code:-
SELECT CONCAT(pub_city,'--> ',country)
FROM publisher;