Combining conditions and Boolean Operators
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.
SELECT column1,
SUM(column2)
FROM "list-of-tables"
WHERE "condition1" AND
"condition2";
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
- 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.
- 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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