MySQl Create Function to checking if string is correct - mysql

Question

I try to create function in mysql. I want to check if the input string correct is (return 1) or not (return 0)
String ist correct when:
-has 3(big letters) to 8 symbols XXaZzzza:
- X are either A-Z or a-z or 0-9
- a could doesn't exsist or is a-z or A-Z
- Z is 0-9
- z could doesn't exsist or is 0-9
I know that code should be like this:
CREATE FUNCTION ID(ID INT)
RETURNS INT
BEGIN
DECLARE {CODE}
RETURN ;
END //
DELIMITER ;
But I don't now how to check this string at all
I tryed with:
CREATE FUNCTION ID(ID INT)
RETURNS char
BEGIN
DECLARE Num char;
IF NUM REGEXP '^([a-zA-Z0-9]{2}[0a-zA-Z]?[0-9][0-9]?[0-9]?[0-9]?[0a-zA-Z]?)' THEN Return "1";
ELSE Return 0;
END IF;
RETURN Num;
END;
But still doesn't work, Returns for all input "0"

Answer 1

You can do this with a regular expression:
select (str regexp '^[A-Z]{3}[a-zA-Z0-9]{2}[a-zA-Z]?[a-zA-Z0-9][0-9]{1,4}[a-zA-Z]?$')
Be sure the column has a case-sensitive collation, if you want to distinguish between upper and lower cases of characters.
Here is an example of it working.

Answer 2

Try a regular expresion in mysql. I´ve been testing it online, perhaps not quite there:
^([a-zA-Z0-9]{2}[0a-zA-Z]?[0-9][0-9]?[0-9]?[0-9]?[0a-zA-Z]?)
This regex checks for everything you stated except those 2 first conditions - 3 capital letters and 8 characters.
If you need user input on your query, use something like:
select regexp_like(:input, '^[a-zA-Z0-9]{2}[0a-zA-Z]?[0-9][0-9]?[0-9]?[0-9]?[0a-zA-Z]?$');
DROP FUNCTION IF EXISTS `test` $$
CREATE FUNCTION `test` (param INT) RETURNS INT(1)
BEGIN
IF EXISTS (select str regexp '^[A-Z]{3}[a-zA-Z0-9]{2}[a-zA-Z]?[a-zA-Z0-9][0-9]{1,4}[a-zA-Z]?$'
from (select param as str) x)
Then
return 1;
ELSE
return 0;
ENDIF