Boolean logic: Difference between revisions

Revision as of 20:57, 14 January 2011

Revision as of 21:10, 14 January 2011

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SELECT * FROM employees WHERE last_name = 'Dean' AND first_name = 'James' ;

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This example will produce a list of all employees, and only those employees, named James Dean.

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SELECT * FROM employees WHERE last_name = 'Dean' OR first_name = 'James' ;

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This example will produce a list of all employees whose first name is James OR whose last name is Dean. Any and all employees named James Dean (from the first example) would also appear in this list.

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SELECT * FROM employees WHERE NOT last_name = 'Dean' ;

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This example will produce a list of all employees whose last name is not Dean. All employees named James from the second example would appear on this list, except for those employees named James Dean.

The first example will produce a list of all employees named James Dean, the second example will produce a list of all employees whose first name is James OR whose last name is Dean, and the third example will produce a list of all employees whose last name is not Dean.

Parentheses may be used to explicitly specify the order in which Boolean operations occur, when multiple operations are present:

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