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PostgreSQL Reference Manual - Volume 1 - SQL Language Reference
by The PostgreSQL Global Development Group
Paperback (6"x9"), 716 pages
ISBN 0954612027
RRP £32.00 ($49.95)

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7.1 Logical Operators

The usual logical operators are available:

SQL uses a three-valued Boolean logic where the null value represents “unknown”. Observe the following truth tables:

a b a AND b a OR b
TRUE TRUE TRUE TRUE
TRUE FALSE FALSE TRUE
TRUE NULL NULL TRUE
FALSE FALSE FALSE FALSE
FALSE NULL FALSE NULL
NULL NULL NULL NULL
a NOT a
TRUE FALSE
FALSE TRUE
NULL NULL
The operators AND and OR are commutative, that is, you can switch the left and right operand without affecting the result. But see section 2.2.12 Expression Evaluation Rules for more information about the order of evaluation of subexpressions.
ISBN 0954612027PostgreSQL Reference Manual - Volume 1 - SQL Language ReferenceSee the print edition