Handling Multi-Byte Character Encoding for Case Conversion in MySQL
Converting Strings to Lowercase in MySQL
- LOWER(string): This function converts all characters in the
string
argument to lowercase. - LCASE(string): This function is functionally identical to
LOWER(string)
. Both return the same result.
Example:
SELECT LOWER('HeLlO WoRlD!'); -- Output: 'hello world!'
SELECT LCASE('ThIs Is A MiXeD cAsE sTrInG'); -- Output: 'this is a mixed case string'
Related Issues and Solutions:
- Case-insensitive comparisons: If you want to perform case-insensitive comparisons in your queries, combine the
LOWER
function with your comparison operator. For example:
SELECT * FROM users WHERE LOWER(username) = 'johndoe';
- Multi-byte character sets: While
LOWER
andLCASE
work well with basic ASCII characters, they might not handle multi-byte encodings like UTF-8 correctly. For accurate conversion with multi-byte characters, use themb_convert_case
function. This function is part of the MySQL extension for PHP, not a native MySQL function.
Example using mb_convert_case
in PHP:
$string = "こんにちは世界"; // "Hello World" in Japanese
$lowercase_string = mb_convert_case($string, MB_CASE_LOWER, 'UTF-8');
echo $lowercase_string; // Output: こんにちはせかい
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