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.