MYSQL: Validate Input Values in Specific Format within a FUNCTION - mysql

Question

i have one question with regard to MYSQL. I want to create a function that is able to check whether an Input is given in a specific format.
The output should be in the following shape:
***x x (a) n (n) (n) (n)
with :
x = letters and numbers
n = numbers
a = letters
brackets = optional Values***
my code is written below this.
CREATE FUNCTION validate_of_number(testnumber VARCHAR(7))
RETURNS INT
DETERMINISTIC
RETURN
CASE
WHEN
(SELECT * FROM flightexecution WHERE FlightNo REGEXP
'^[[:alnum:]+[:alnum:]] + [[:alpha:]|''] + [:digit:] +
[[:digit:]|''] + [[:digit:]|''] + [[:digit:]|'']') > 0
Then 1
Else 0
END;`
However, it does not work and i don´t know why. The Output is just a 'OK' without any further information.

Answer 1

I'm assuming based on your description of valid values and the context of your question that the values you are trying to validate look something like CX727 or QF1566 or BA1 etc (i.e. IATA flight designator codes). In that case, this function will give you the results you want:
CREATE FUNCTION validate_of_number(testnumber VARCHAR(7))
RETURNS INT
DETERMINISTIC
RETURN testnumber REGEXP '^[[:alnum:]]{2}[[:alpha:]]?[[:digit:]]{1,4}$';
Examples:
SELECT validate_of_number('A1B4352')
, validate_of_number('QF12')
, validate_of_number('CX727')
, validate_of_number('AB14352')
, validate_of_number('BA1')
, validate_of_number('1C42')
Output
1, 1, 1, 0, 1, 1
Demo on dbfiddle
In terms of using it with your table you might use a query like
SELECT * FROM flightexecution WHERE validate_of_number(FlightNo)