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?
@ is used as a prefix denoting stored procedure and function parameter names, and also variable names
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.
Its a parameter the you need to define. to prevent SQL Injection you should pass all your variables in as parameters.
You may be used to MySQL's syntax: Microsoft SQL @ is the same as the MySQL's ?
So would you set what @custID's value is inside this select query or before you do the query?
SET @custID = '1';
Something like that?
What you are talking about is the way a parameterized query is written. '@' just signifies that it is a parameter. You can add the value for that parameter during execution process
eg:
sqlcommand cmd = new sqlcommand(query,connection);
cmd.parameters.add("@custid","1");
sqldatareader dr = cmd.executequery();