Question

I was browsing through the questions and noticed this:

SELECT prodid, issue FROM Sales  WHERE custid = @custid  AND datesold = SELECT MAX(datesold)               FROM Sales s               WHERE s.prodid = Sales.prodid                   AND s.issue = Sales.issue                   AND s.custid = @custid 

I was wondering what the ‘@’ does in front of custID? Is it just a way of referencing the custID from the table being selected?

Answer 1

The @CustID means it’s a parameter that you will supply a value for later in your code. This is the best way of protecting against SQL injection. Create your query using parameters, rather than concatenating strings and variables. The database engine puts the parameter value into where the placeholder is, and there is zero chance for SQL injection.