Function to retrieve the Id column

Hi list,

 

I have Id field that is used in all my database but my more often used parameter is a column called "number" that I have in more than 5000 magnetic cards, my question is.

 

How could I make a function to retrieve this Id just passing the number as parameter, just like:

 

getCardId(number: varchar)

 

 

Best regards ...

Ezequias