SQL Count

The SQL Count is an important function that I use when I am exploring a new table.

I often use it to see how big a table is, but I also use it to determine counts within a group.

Let-s take a look at it-s uses.

Here is the employee table:

select *

from employee;

Results:

![Select Results](../../assets/blog/2012/06/image_thumb21.png)

You can tell this has 14 records, but imagine that it had 1,000,000 records.

You wouldn-t be able to just **select *** without it taking a while to bring all of the records back.

That is where the **SQL Count** comes in:

select count(*)

from employee;

![SQL Count * Results](../../assets/blog/2012/06/image_thumb22.png)

Here you can see it gave us one column with the count of the whole table.

Pretty simple.

Now, what if we wanted to find out how many people had a commission?

If we look above, we can simply count those people. But, we have this new SQL Count function.

So, let-s use it:

select count(commision)

from employee;

Will we get 14 records, or 4 records?

Well, here are the results:

We only got 4 records. Why is that-?

That is because the count function doesn-t count NULL records. Again, if you look above, you will see a bunch of commissions that have the value of NULL.

This NULL value means we don-t have a value. So, when the SQL Count function looks at those rows, it ignores them.

But, look at the 10th row above. It has a -0.00- value. Why does it count that one?

Because, even though the value is 0, it is still a value (it isn-t null).

An that-s it. That-s how you use the **SQL Count **function.