> This Function will takes a string and give:
> 0000-00-00 if string cannot be converted (string in <> date out)
> NULL if String NULL or blank(string in = date out)
> yyyy-mm-dd if string can be converted (string in = date out)
Drop function if exists stringtodate;
DELIMITER $$
CREATE FUNCTION `stringtodate`(v TEXT) Returns DATE
BEGIN
DECLARE result DATE;
IF (v Is Null or v = '') THEN SET result = NULL;
ELSEIF (STR_TO_DATE(v,'%d-%m-%Y') IS NOT NULL AND length(clean(v)) > 8) THEN SET result = STR_TO_DATE(v,'%d-%m-%Y');
ELSEIF (STR_TO_DATE(v,'%d,%m,%Y') IS NOT NULL AND length(clean(v)) > 8) THEN SET result = STR_TO_DATE(v,'%d,%m,%Y');
ELSEIF (STR_TO_DATE(v,'%d/%m/%Y') IS NOT NULL AND length(clean(v)) > 8) THEN SET result = STR_TO_DATE(v,'%d/%m/%Y');
ELSEIF (STR_TO_DATE(v,'%Y-%m-%d') IS NOT NULL AND length(clean(v)) > 8) THEN SET result = STR_TO_DATE(v,'%Y-%m-%d');
ELSEIF (STR_TO_DATE(v,'%Y,%m,%d') IS NOT NULL AND length(clean(v)) > 8) THEN SET result = STR_TO_DATE(v,'%Y,%m,%d');
ELSEIF (STR_TO_DATE(v,'%Y/%m/%d') IS NOT NULL AND length(clean(v)) > 8) THEN SET result = STR_TO_DATE(v,'%Y/%m/%d');
ELSEIF (STR_TO_DATE(v,'%d-%m-%y') IS NOT NULL AND length(clean(v)) < 10) THEN SET result = STR_TO_DATE(v,'%d-%m-%y');
ELSEIF (STR_TO_DATE(v,'%d,%m,%y') IS NOT NULL AND length(clean(v)) < 10) THEN SET result = STR_TO_DATE(v,'%d,%m,%y');
ELSEIF (STR_TO_DATE(v,'%d/%m/%y') IS NOT NULL AND length(clean(v)) < 10) THEN SET result = STR_TO_DATE(v,'%d/%m/%y');
ELSE SET result = CAST("0000-00-00" AS DATE);
END IF;
Return result;
END