SQL Where

The SQL Where clause in the SQL Language allows you to filter data when you query a database.

Let’s look at the following query that gets data from the customer table:

select * from customer; 

Here are the results:

Now, I only need to get the “Dell” customers.  In order to do that, I have to use the where clause.

Let’s add that to the query:

select * from customer where customer_company='Dell'; 

When I execute this query, I get the following results:

So I have filtered the records from 6 down to 2.

Notice the following part of the query:

customer_company='Dell'; 

The red part is how Microsoft SQL Server represents a string.  It knows it is a string, because of the single tick (‘) marks.

All strings need to be enclosed in these.

Let’s show an example where we want everyone except for Dell customers:

select * from customer where customer_company != 'Dell'; 

Instead of using the “=” sign, we use the “!=” which says “Not Equal”.

Here are the results:

We have filtered out the 2 Dell records.

That is the basics of the where clause.

Please leave any comments or questions below.