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    PolarDB:Logical operators

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    PolarDB:Logical operators

    Last Updated:Aug 02, 2024

    This topic describes the logical operators supported by PolarDB for PostgreSQL (Compatible with Oracle).

    The usual logical operators are available: 

        boolean AND boolean → boolean
    boolean OR boolean → boolean
    NOT boolean → boolean

    SQLuses a three-valued logic system with true, false, and null, which 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 operands without affecting the result. (However, it is not guaranteed that the left operand is evaluated before the right operand.