Comparison Operations

The following operations can take operands with multiple data types but always return a Boolean value (sometimes nullable):

Comparison Operations

Operation	Definition	Observation
=	equality test
<>	inequality test
!=	inequality test, same as above
>	greater than
<	less than
>=	greater or equal
<=	less or equal
IS NULL	true if operand is NULL
IS NOT NULL	true if operand is not NULL
<=>	equality check that treats NULL values as equal	result is not nullable
IS DISTINCT FROM	check if two values are not equal, treating NULL as equal	result is not nullable
IS NOT DISTINCT FROM	check if two values are the same, treating NULL values as equal	result is not nullable
BETWEEN ... AND ...	x BETWEEN a AND b is the same as a <= x AND x <= b	inclusive at both endpoints
NOT BETWEEN ... AND ...	The NOT of the previous operator	not inclusive at either endpoint
... IN ...	checks whether value appears in a list or set
<OP> ANY set_or_subquery	check if any of the values in a set compares properly	Example: 10 <= ANY (VALUES 10, 20, 30) is true
<OP> SOME set_or_subquery	A synonym for ANY	Example: 10 <= SOME (VALUES 10, 20, 30) is true
<OP> ALL set_or_subquery	check if all the values in a set compare properly	Example: 10 <= ALL (VALUES 10, 20, 30) is true
EXISTS query	check whether query results have at least one row
UNIQUE query	check whether the result of a query contains no duplicates	ignores NULL values

Note that the SQL standard mandates IS NULL to return true for a ROW object where all fields are NULL (similarly, IS NOT NULL is required to return false). Our compiler diverges from the standard, returning false for ROW(null) is null.

Comparison operations (=, <>, !=, <, >, <=, >=, <=>, IS NULL, IS NOT NULL) are defined on all data types, even recursive data types (including ARRAY, MAP, ROW, VARIANT, user-defined types). For complex types, comparisons are performed lexicographically on the type structure. In such comparisons fields with NULL values are compared smaller than any other value.

Other conditional operators

CASE value WHEN value1 [, value11 ]* THEN result1 [ WHEN valueN [, valueN1 ]* THEN resultN ]* [ ELSE resultZ ] END	Simple case
CASE WHEN condition1 THEN result1 [ WHEN conditionN THEN resultN ]* [ ELSE resultZ ] END	Searched case
NULLIF(value, value)	Returns NULL if the values are the same. For example, NULLIF(5, 5) returns NULL; NULLIF(5, 0) returns 5.
COALESCE(value, value [, value ]*)	Provides a value if the first value is NULL. For example, COALESCE(NULL, 5) returns 5.