Help Center/ GaussDB/ Developer Guide(Distributed_V2.0-3.x)/ SQL Reference/ Functions and Operators/ Logical Operators
Updated on 2025-08-19 GMT+08:00
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Logical Operators

The usual logical operators include AND, OR, and NOT. SQL uses a three-valued logical system with true, false, and null, which represents "unknown". Their priorities are NOT > AND > OR.

Table 1 lists the calculation rules, where a and b represent logical expressions.

Table 1 Operation rules

a

b

a AND b Result

a OR b Result

NOT a Result

TRUE

TRUE

TRUE

TRUE

FALSE

TRUE

FALSE

FALSE

TRUE

FALSE

TRUE

NULL

NULL

TRUE

FALSE

FALSE

FALSE

FALSE

FALSE

TRUE

FALSE

NULL

FALSE

NULL

TRUE

NULL

NULL

NULL

NULL

NULL
  • The operators AND and OR are commutative, that is, you can switch the left and right operand without affecting the result.
  • Operations on XML data are not supported.
Parent topic: Functions and Operators