MySQL Function to remove accents and special characters

fn_remove_accents.sql

DROP FUNCTION IF EXISTS fn_remove_accents;
DELIMITER |
CREATE FUNCTION fn_remove_accents( textvalue VARCHAR(10000) ) RETURNS VARCHAR(10000)

BEGIN

    SET @textvalue = textvalue COLLATE utf8_general_ci;;

    -- ACCENTS
    SET @withaccents = 'ŠšŽžÀÁÂÃÄÅÆÇÈÉÊËÌÍÎÏÑÒÓÔÕÖØÙÚÛÜÝŸÞàáâãäåæçèéêëìíîïñòóôõöøùúûüýÿþƒ';
    SET @withoutaccents = 'SsZzAAAAAAACEEEEIIIINOOOOOOUUUUYYBaaaaaaaceeeeiiiinoooooouuuuyybf';
    SET @count = LENGTH(@withaccents);

    WHILE @count > 0 DO
        SET @textvalue = REPLACE(@textvalue, SUBSTRING(@withaccents, @count, 1), SUBSTRING(@withoutaccents, @count, 1));
        SET @count = @count - 1;
    END WHILE;

    -- SPECIAL CHARS
    SET @special = '«»’”“!@#$%¨&()_+=§¹²³£¢¬"`´{[^~}]<,>.:;?/°ºª+|\''';
    SET @count = LENGTH(@special);
    
    WHILE @count > 0 do
        SET @textvalue = REPLACE(@textvalue, SUBSTRING(@special, @count, 1), '');
        SET @count = @count - 1;
    END WHILE;

    RETURN @textvalue;

END
|
DELIMITER ;

First of all, thanks for good job jgdoncel.
for Vietnamese try this function. I modified a little bit @withaccents & @withoutaccents value to map with Tiếng Việt.

`DROP FUNCTION IF EXISTS fn_remove_accents;
DELIMITER |
CREATE FUNCTION fn_remove_accents( textvalue VARCHAR(10000) ) RETURNS VARCHAR(10000)

BEGIN

SET @textvalue = textvalue ;

-- ACCENTS
SET @withaccents = 'ăâđêôơưàảãạáằẳẵặắầẩẫậấèẻẽẹéềểễệếìỉĩịíòỏõọóồổỗộốờởỡợớùủũụúừửữựứỳỷỹỵýĂÂĐÊÔƠƯÀẢÃẠÁẰẲẴẶẮẦẨẪẬẤÈẺẼẸÉỀỂỄỆẾÌỈĨỊÍÒỎÕỌÓỒỔỖỘỐỜỞỠỢỚÙỦŨỤÚỪỬỮỰỨỲỶỸỴÝ';
SET @withoutaccents = 'aadeoouaaaaaaaaaaaaaaaeeeeeeeeeeiiiiiooooooooooooooouuuuuuuuuuyyyyyAADEOOUAAAAAAAAAAAAAAAEEEEEEEEEEIIIIIOOOOOOOOOOOOOOOUUUUUUUUUUYYYYY';
SET @count = LENGTH(@withaccents);

WHILE @count > 0 DO
SET @textvalue = REPLACE(@textvalue, SUBSTRING(@withaccents, @count, 1), SUBSTRING(@withoutaccents, @count, 1));
SET @count = @count - 1;
END WHILE;

-- SPECIAL CHARS
SET @special = '«»’”“!@#$%¨&()_+=§¹²³£¢¬"`´{[^~}]<,>.:;?/°ºª+|'';
SET @count = LENGTH(@special);

WHILE @count > 0 do
SET @textvalue = REPLACE(@textvalue, SUBSTRING(@special, @count, 1), '');
SET @count = @count - 1;
END WHILE;
RETURN @textvalue;
END
|
DELIMITER ;
`

I use in Azure Data Studio the next (only for symbols):

DROP FUNCTION IF EXISTS REMOVE_SYMBOLS;

CREATE FUNCTION REMOVE_SYMBOLS( text_value TEXT(100) )
RETURNS TEXT(100) DETERMINISTIC

BEGIN
SET @text_value = text_value COLLATE utf8_general_ci;
-- SPECIAL CHARS
-- Use the escape character \ before the single quote'
SET @special = '«»’”“!@#$%¨&()_+=§¹²³£¢¬"`´{[^~}]<,>.:;?/°ºª#+.-*|'';
SET @count = LENGTH(@special);

WHILE @count > 0 do
    SET @text_value = REPLACE(@text_value, SUBSTRING(@special, @count, 1), '');
    SET @count = @count - 1;
END WHILE;
RETURN @text_value;

END