Syntax:
LOWER(str)

Returns the string str with all characters changed to lowercase
according to the current character set mapping. The default is latin1
(cp1252 West European).

mysql> SELECT LOWER('QUADRATICALLY');
        -> 'quadratically'

LOWER() (and UPPER()) are ineffective when applied to binary strings
(BINARY, VARBINARY, BLOB). To perform lettercase conversion, convert
the string to a nonbinary string:

mysql> SET @str = BINARY 'New York';
mysql> SELECT LOWER(@str), LOWER(CONVERT(@str USING latin1));
+-------------+-----------------------------------+
| LOWER(@str) | LOWER(CONVERT(@str USING latin1)) |
+-------------+-----------------------------------+
| New York    | new york                          |
+-------------+-----------------------------------+

For Unicode character sets, LOWER() and UPPER() work accounting to
Unicode Collation Algorithm (UCA) 5.2.0 for xxx_unicode_520_ci
collations and for language-specific collations that are derived from
them. For other Unicode collations, LOWER() and UPPER() work accounting
to Unicode Collation Algorithm (UCA) 4.0.0. See
http://dev.mysql.com/doc/refman/5.6/en/charset-unicode-sets.html.

URL: http://dev.mysql.com/doc/refman/5.6/en/string-functions.html

