Combining conditions and
Boolean Operators
SELECT column1, SUM(column2) FROM "list-of-tables" WHERE
"condition1" AND "condition2";
The AND operator can be used to join two or more conditions in
the WHERE clause. Both sides of the AND condition must be true in
order for the condition to be met and for those rows to be
displayed.
The OR operator can be used to join two or more conditions in the
WHERE clause also. However, either side of the OR operator
can be true and the condition will be met - hence, the rows will be
displayed. With the OR operator, either side can be true or both
sides can be true.
For example:
SELECT employeeid, firstname, lastname, title, salary FROM
employee_info WHERE salary >= 50000.00 AND title =
'Programmer';
This statement will select the employeeid, firstname, lastname,
title, and salary from the employee_info table where the salary is
greater than or equal to 50000.00 AND the title is equal to
'Programmer'. Both of these conditions must be true in order for the
rows to be returned in the query. If either is false, then it will
not be displayed.
Although they are not required, you can use paranthesis around
your conditional expressions to make it easier to read:
SELECT employeeid, firstname, lastname, title, salary FROM
employee_info WHERE (salary >= 50000.00) AND (title =
'Programmer');
Another Example:
SELECT firstname, lastname, title, salary FROM
employee_info WHERE (title = 'Sales') OR (title = 'Programmer');
This statement will select the firstname, lastname, title, and
salary from the employee_info table where the title is either equal
to 'Sales' OR the title is equal to 'Programmer'.
Review Exercises
1) Select the customerid, order_date, and item from the
items_ordered table for all items unless they are 'Snow Shoes' or if
they are 'Ear Muffs'. Display the rows as long as they are not
either of these two items.
2) Select the item and price of all items that start with the
letters 'S', 'P', or 'F'.
Click the exercise answers link below if you have any problems.
Answers to
these Exercises
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