[Ajaxx]

I’m trying to create an MS SQL DAL for my plugin. I have it working as in I’m able to pass parameters to my stored procedures and return a recordset. But it seems kind of clunky and I can’t really tell the difference between returning 0 (as in the int) and returning NULL (as in no recordset). Has anyone already created a DAL I can use or have some examples for best practices I can follow?

[recon0]

NULL is 0.

As for DALs, SourceMod might have some interesting code for you to look at.

[Ajaxx]

I know NULL is 0 that’s the point. How do you tell the difference? Say you have a function that looks up an int in the database and returns it. So the function has a return value of int. In your database you have a table that looks like this:

 
Name  Value
A       1
B       0

How do you tell the difference between:

SELECT Value FROM Table WHERE Name = B

And

SELECT Value FROM Table WHERE Name = C

When C isn’t found it’s going to return NULL but this is the same as returning 0 or the same result as a query for B.

I don’t want my DAL to return a variant when I know the return type is an int or a double or whatever. Maybe I’m going about this the wrong way. Maybe I should just setup my database to never have a 0 in an int field. But this doesn’t seem right.

SourceMod has a provider for MySQL I believe, I was looking for a MS SQL provider.

I’m just looking for something really simple, a DAL you pass the SP name and parameters to and it gives you back an int, double, string, date, or record set. Is there such a thing as nullable types in C++?

I don’t know what that guy in the other thread was talking about I always get a helpful answer here!

[recon0]

Originally Posted by Ajaxx I know NULL is 0 that’s the point. How do you tell the difference? Is there such a thing as nullable types in C++?

You can't. Consider:

PHP Code:

// This is how NULL is defined
#define NULL 0

// NULL is an integer
int i = 0;

// This is true
i == NULL 


Not in the standard library. Boost doesn't seem to have them either.

You could write your own nullable type class. Just be careful not to create a magic number when you define your NULL (DB_NULL perhaps). A pointer to a singleton could work.

[L. Duke]

Generally when working with a database you will first check to make sure that the record count is greater than zero. Then when you get the result after that you know that it is a valid number.