Beginning SQL the SEQUEL: Working with Advanced SQL Statements - AND and OR...Or OR and And
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If it's any comfort, that title hurt my head typing it as much as it did yours reading it. In the previous tutorial we spoke about the WHERE CLAUSE and its uses. Here, we will go a little more in-depth and add some power to it using the AND and OR operators.

AND

Say you wanted to list all the people in our employee database that had the first name Homer and the last name Sampson (if you remember in the first tutorial I had you add Homer's twin brother, Homer, to the table). One way we could do this is by joining the WHERE clause with the AND operator (think Voltron with words).

SELECT * from EMPLOYEES

WHERE FirstName='Homer'

AND LastName='Sampson';

The above sample would return the following dataset:

First Name	Last Name	Position	Salary
Homer	Sampson	CEO	$75,000
Homer	Sampson	CFO	$75,000

So let's say that Homer Sampson has a daughter, we'll call her, I don't know...Liza (to avoid a lawsuit from Matt Groening and Sam Simon). She isn't married yet because she is a high-powered business woman, devoted to her job, so her last name is still Sampson. Her salary is a little more than her father's, because she is the CTO and daddy's little baby. So let's give her $85,000 a year. Go ahead and add her to the employee table.

OR

Now that we have added Liza Sampson to our employee table, let's do some more coding. In this example, we want to list all people with either the first name Liza, or the last name of Sampson.

SELECT * from EMPLOYEES

WHERE FirstName="Liza'

OR LastName='Sampson";

Here's how that should look in your table:

First Name	Last Name	Position	Salary
Homer	Sampson	CEO	$75,000
Homer	Sampson	CFO	$75,000
Liza	Sampson	CTO	$85,000

Lastly, you can combine the might of the AND and OR statements. I know -- how can one man wield that much power? Well you can -- and will -- with the following code.

SELECT * from EMPLOYEES WHERE

(FirstName='Liza' OR FirstName='Homer')

AND LastName='Sampson';

This code will return the same results as above.

First Name	Last Name	Position	Salary
Homer	Sampson	CEO	$75,000
Homer	Sampson	CFO	$75,000
Liza	Sampson	CTO	$85,000

Next: The IN-credible Statement >>
 

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