How to: using SQL conditions and Boolean Operators

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'.

NOTE: How to: using SQL conditions and Boolean Operators

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