11th October 2018: PostgreSQL 11 RC 1 Released!
Supported Versions: Current (10) / 9.6 / 9.5 / 9.4 / 9.3
Development Versions: 11 / devel
Unsupported versions: 9.2 / 9.1 / 9.0 / 8.4 / 8.3 / 8.2 / 8.1 / 8.0 / 7.4

# 9.17. Array Functions and Operators

Table 9-41 shows the operators available for array types.

Table 9-41. Array Operators

Operator Description Example Result
= equal ARRAY[1.1,2.1,3.1]::int[] = ARRAY[1,2,3] t
<> not equal ARRAY[1,2,3] <> ARRAY[1,2,4] t
< less than ARRAY[1,2,3] < ARRAY[1,2,4] t
> greater than ARRAY[1,4,3] > ARRAY[1,2,4] t
<= less than or equal ARRAY[1,2,3] <= ARRAY[1,2,3] t
>= greater than or equal ARRAY[1,4,3] >= ARRAY[1,4,3] t
@> contains ARRAY[1,4,3] @> ARRAY[3,1] t
<@ is contained by ARRAY[2,7] <@ ARRAY[1,7,4,2,6] t
&& overlap (have elements in common) ARRAY[1,4,3] && ARRAY[2,1] t
|| array-to-array concatenation ARRAY[1,2,3] || ARRAY[4,5,6] {1,2,3,4,5,6}
|| array-to-array concatenation ARRAY[1,2,3] || ARRAY[[4,5,6],[7,8,9]] {{1,2,3},{4,5,6},{7,8,9}}
|| element-to-array concatenation 3 || ARRAY[4,5,6] {3,4,5,6}
|| array-to-element concatenation ARRAY[4,5,6] || 7 {4,5,6,7}

Array comparisons compare the array contents element-by-element, using the default B-tree comparison function for the element data type. In multidimensional arrays the elements are visited in row-major order (last subscript varies most rapidly). If the contents of two arrays are equal but the dimensionality is different, the first difference in the dimensionality information determines the sort order. (This is a change from versions of PostgreSQL prior to 8.2: older versions would claim that two arrays with the same contents were equal, even if the number of dimensions or subscript ranges were different.)

See Section 8.14 for more details about array operator behavior.

Table 9-42 shows the functions available for use with array types. See Section 8.14 for more information and examples of the use of these functions.

Table 9-42. Array Functions

Function Return Type Description Example Result
`array_append`(anyarray, anyelement) anyarray append an element to the end of an array array_append(ARRAY[1,2], 3) {1,2,3}
`array_cat`(anyarray, anyarray) anyarray concatenate two arrays array_cat(ARRAY[1,2,3], ARRAY[4,5]) {1,2,3,4,5}
`array_ndims`(anyarray) int returns the number of dimensions of the array array_ndims(ARRAY[[1,2,3], [4,5,6]]) 2
`array_dims`(anyarray) text returns a text representation of array's dimensions array_dims(ARRAY[[1,2,3], [4,5,6]]) [1:2][1:3]
`array_fill`(anyelement, int[], [, int[]]) anyarray returns an array initialized with supplied value and dimensions, optionally with lower bounds other than 1 array_fill(7, ARRAY[3], ARRAY[2]) [2:4]={7,7,7}
`array_length`(anyarray, int) int returns the length of the requested array dimension array_length(array[1,2,3], 1) 3
`array_lower`(anyarray, int) int returns lower bound of the requested array dimension array_lower('[0:2]={1,2,3}'::int[], 1) 0
`array_prepend`(anyelement, anyarray) anyarray append an element to the beginning of an array array_prepend(1, ARRAY[2,3]) {1,2,3}
`array_to_string`(anyarray, text) text concatenates array elements using supplied delimiter array_to_string(ARRAY[1, 2, 3], '~^~') 1~^~2~^~3
`array_upper`(anyarray, int) int returns upper bound of the requested array dimension array_upper(ARRAY[1,2,3,4], 1) 4
`string_to_array`(text, text) text[] splits string into array elements using supplied delimiter string_to_array('xx~^~yy~^~zz', '~^~') {xx,yy,zz}
`unnest`(anyarray) setof anyelement expand an array to a set of rows unnest(ARRAY[1,2]) 1

2

(2 rows)

See also Section 9.18 about the aggregate function `array_agg` for use with arrays.