9.19. 範圍函式及運算子

SeeSection 8.17for an overview of range types.

Table 9.50shows the operators available for range types.

Table 9.50. Range Operators

Operator	Description	Example	Result
=	equal	int4range(1,5) = '[1,4]'::int4range	t
<>	not equal	numrange(1.1,2.2) <> numrange(1.1,2.3)	t
<	less than	int4range(1,10) < int4range(2,3)	t
>	greater than	int4range(1,10) > int4range(1,5)	t
<=	less than or equal	numrange(1.1,2.2) <= numrange(1.1,2.2)	t
>=	greater than or equal	numrange(1.1,2.2) >= numrange(1.1,2.0)	t
@>	contains range	int4range(2,4) @> int4range(2,3)	t
@>	contains element	'[2011-01-01,2011-03-01)'::tsrange @> '2011-01-10'::timestamp	t
<@	range is contained by	int4range(2,4) <@ int4range(1,7)	t
<@	element is contained by	42 <@ int4range(1,7)	f
&&	overlap (have points in common)	int8range(3,7) && int8range(4,12)	t
<<	strictly left of	int8range(1,10) << int8range(100,110)	t
>>	strictly right of	int8range(50,60) >> int8range(20,30)	t
&<	does not extend to the right of	int8range(1,20) &< int8range(18,20)	t
&>	does not extend to the left of	int8range(7,20) &> int8range(5,10)	t
`-	-`	is adjacent to	`numrange(1.1,2.2) -	- numrange(2.2,3.3)`	t
+	union	numrange(5,15) + numrange(10,20)	[5,20)
*	intersection	int8range(5,15) * int8range(10,20)	[10,15)
-	difference	int8range(5,15) - int8range(10,20)	[5,10)

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 9.51shows the functions available for use with range types.

Table 9.51. 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
range_merge(anyrange,anyrange)	anyrange	the smallest range which includes both of the given ranges	range_merge('[1,2)'::int4range, '[3,4)'::int4range)	[1,4)

Thelowerandupperfunctions return null if the range is empty or the requested bound is infinite. Thelower_inc,upper_inc,lower_inf, andupper_inffunctions all return false for an empty range.