SQL AND OR

The SQL AND OR is used when filtering with the SQL Where clause.  More specifically, we are talking about the “AND” and the “OR” clauses.

Let’s start by looking at a basic SQL statement:

select * from customer 

The customer table has the following records:

Now if we were to filter to just the “Dell” records, we would use the following query:

select * 
from customer 
where customer_company = 'Dell'; 

But, I want to get the “Dell” records and the “HP” records.  To do that we would use the following query:

select * 
from customer 
where customer_company = 'Dell' 
 or customer_company='HP'; 

And we get the following results:

Now, you are probably asking, “You said we want Dell AND HP records, why did we use the OR clause?”

It can be a little confusing, but here is how I think of it.

In the case where we want the company of Dell and HP, we are actually saying we want all of the records where the customer_company is Dell or the customer company is HP.

There is a never a case where the customer_company is both Dell and HP.

So let’s look at an example where we use the AND statement.

If, I wanted to get all of the Dell customers that have a name of Bill, I would use the following query:

select * 
from customer 
where customer_company = 'Dell' 
 and customer_name='Bill'; 

In this case, I am actually looking for records where both criteria is met.  Here is the result:

Those are the basics of using the SQL AND and OR clauses.

Please leave and questions or comments below and let me know if you want me to talk about any other topics.