The simple comparison operators <,
>, <=, and
>= compare the lower bounds first, and only if those
are equal, compare the upper bounds. These comparisons are not usually
very useful for ranges, but are provided to allow B-tree indexes to be
constructed on ranges.
The left-of/right-of/adjacent operators always return false when an empty
range is involved; that is, an empty range is not considered to be either
before or after any other range.
The union and difference operators will fail if the resulting range would
need to contain two disjoint sub-ranges, as such a range cannot be
represented.
Table 9-45 shows the functions
available for use with range types.
Table 9-45. Range Functions
Function
Return Type
Description
Example
Result
lower(anyrange)
range's element type
lower bound of range
lower(numrange(1.1,2.2))
1.1
upper(anyrange)
range's element type
upper bound of range
upper(numrange(1.1,2.2))
2.2
isempty(anyrange)
boolean
is the range empty?
isempty(numrange(1.1,2.2))
false
lower_inc(anyrange)
boolean
is the lower bound inclusive?
lower_inc(numrange(1.1,2.2))
true
upper_inc(anyrange)
boolean
is the upper bound inclusive?
upper_inc(numrange(1.1,2.2))
false
lower_inf(anyrange)
boolean
is the lower bound infinite?
lower_inf('(,)'::daterange)
true
upper_inf(anyrange)
boolean
is the upper bound infinite?
upper_inf('(,)'::daterange)
true
The lower and upper functions return null
if the range is empty or the requested bound is infinite.
The lower_inc, upper_inc,
lower_inf, and upper_inf
functions all return false for an empty range.