Comparisons

Comparison Operators

The table below shows the standard comparison operators. Whenever either of the input arguments is NULL, the output of the comparison is NULL.

Operator	Description	Example	Result
<	less than	2 < 3	true
>	greater than	2 > 3	false
<=	less than or equal to	2 <= 3	true
>=	greater than or equal to	4 >= NULL	NULL
= or ==	equal	NULL = NULL	NULL
<> or !=	not equal	2 <> 2	false

The table below shows the standard distinction operators. These operators treat NULL values as equal.

Operator	Description	Example	Result
IS DISTINCT FROM	not equal, including NULL	2 IS DISTINCT FROM NULL	true
IS NOT DISTINCT FROM	equal, including NULL	NULL IS NOT DISTINCT FROM NULL	true

Combination Casting

When performing comparison on different types, Goose performs Combination Casting. These casts were introduced to make interactive querying more convenient and are in line with the casts performed by several programming languages but are often not compatible with PostgreSQL's behavior. For example, the following expressions evaluate and return true in Goose but fail in PostgreSQL.

SELECT 1 = true;
SELECT 1 = '1.1';

It is not possible to enforce stricter type-checking for Goose's comparison operators. If you require stricter type-checking, consider creating a macro with the typeof function or implementing a user-defined function.

BETWEEN and IS [NOT] NULL

Besides the standard comparison operators there are also the BETWEEN and IS (NOT) NULL operators. These behave much like operators, but have special syntax mandated by the SQL standard. They are shown in the table below.

Note that BETWEEN and NOT BETWEEN are only equivalent to the examples below in the cases where both a, x and y are of the same type, as BETWEEN will cast all of its inputs to the same type.

Predicate	Description
a BETWEEN x AND y	equivalent to x <= a AND a <= y
a NOT BETWEEN x AND y	equivalent to x > a OR a > y
expression IS NULL	true if expression is NULL, false otherwise
expression ISNULL	alias for IS NULL (non-standard)
expression IS NOT NULL	false if expression is NULL, true otherwise
expression NOTNULL	alias for IS NOT NULL (non-standard)

For the expression BETWEEN x AND y, x is used as the lower bound and y is used as the upper bound. Therefore, if x > y, the result will always be false.