shows the specialized operators available for array types. In addition to those, the usual comparison operators shown in are available for arrays. The comparison operators compare the array contents element-by-element, using the default B-tree comparison function for the element data type, and sort based on the first difference. 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. Operator Description Example(s) anyarray @> anyarray boolean Does the first array contain the second, that is, does each element appearing in the second array equal some element of the first array? (Duplicates are not treated specially, thus ARRAY[1] and ARRAY[1,1] are each considered to contain the other.) ARRAY[1,4,3] @> ARRAY[3,1,3] t anyarray <@ anyarray boolean Is the first array contained by the second? ARRAY[2,2,7] <@ ARRAY[1,7,4,2,6] t anyarray && anyarray boolean Do the arrays overlap, that is, have any elements in common? ARRAY[1,4,3] && ARRAY[2,1] t anycompatiblearray || anycompatiblearray anycompatiblearray Concatenates the two arrays. Concatenating a null or empty array is a no-op; otherwise the arrays must have the same number of dimensions (as illustrated by the first example) or differ in number of dimensions by one (as illustrated by the second). If the arrays are not of identical element types, they will be coerced to a common type (see ). ARRAY[1,2,3] || ARRAY[4,5,6,7] {1,2,3,4,5,6,7} ARRAY[1,2,3] || ARRAY[[4,5,6],[7,8,9.9]] {{1,2,3},{4,5,6},{7,8,9.9}} anycompatible || anycompatiblearray anycompatiblearray Concatenates an element onto the front of an array (which must be empty or one-dimensional). 3 || ARRAY[4,5,6] {3,4,5,6} anycompatiblearray || anycompatible anycompatiblearray Concatenates an element onto the end of an array (which must be empty or one-dimensional). ARRAY[4,5,6] || 7 {4,5,6,7} See for more details about array operator behavior. See for more details about which operators support indexed operations. shows the functions available for use with array types. See for more information and examples of the use of these functions. Function Description Example(s) array_append array_append ( anycompatiblearray, anycompatible ) anycompatiblearray Appends an element to the end of an array (same as the anycompatiblearray || anycompatible operator). array_append(ARRAY[1,2], 3) {1,2,3} array_cat array_cat ( anycompatiblearray, anycompatiblearray ) anycompatiblearray Concatenates two arrays (same as the anycompatiblearray || anycompatiblearray operator). array_cat(ARRAY[1,2,3], ARRAY[4,5]) {1,2,3,4,5} array_dims array_dims ( anyarray ) text Returns a text representation of the array's dimensions. array_dims(ARRAY[[1,2,3], [4,5,6]]) [1:2][1:3] array_fill array_fill ( anyelement, integer[] , integer[] ) anyarray Returns an array filled with copies of the given value, having dimensions of the lengths specified by the second argument. The optional third argument supplies lower-bound values for each dimension (which default to all 1). array_fill(11, ARRAY[2,3]) {{11,11,11},{11,11,11}} array_fill(7, ARRAY[3], ARRAY[2]) [2:4]={7,7,7} array_length array_length ( anyarray, integer ) integer Returns the length of the requested array dimension. (Produces NULL instead of 0 for empty or missing array dimensions.) array_length(array[1,2,3], 1) 3 array_length(array[]::int[], 1) NULL array_length(array['text'], 2) NULL array_lower array_lower ( anyarray, integer ) integer Returns the lower bound of the requested array dimension. array_lower('[0:2]={1,2,3}'::integer[], 1) 0 array_ndims array_ndims ( anyarray ) integer Returns the number of dimensions of the array. array_ndims(ARRAY[[1,2,3], [4,5,6]]) 2 array_position array_position ( anycompatiblearray, anycompatible , integer ) integer Returns the subscript of the first occurrence of the second argument in the array, or NULL if it's not present. If the third argument is given, the search begins at that subscript. The array must be one-dimensional. Comparisons are done using IS NOT DISTINCT FROM semantics, so it is possible to search for NULL. array_position(ARRAY['sun', 'mon', 'tue', 'wed', 'thu', 'fri', 'sat'], 'mon') 2 array_positions array_positions ( anycompatiblearray, anycompatible ) integer[] Returns an array of the subscripts of all occurrences of the second argument in the array given as first argument. The array must be one-dimensional. Comparisons are done using IS NOT DISTINCT FROM semantics, so it is possible to search for NULL. NULL is returned only if the array is NULL; if the value is not found in the array, an empty array is returned. array_positions(ARRAY['A','A','B','A'], 'A') {1,2,4} array_prepend array_prepend ( anycompatible, anycompatiblearray ) anycompatiblearray Prepends an element to the beginning of an array (same as the anycompatible || anycompatiblearray operator). array_prepend(1, ARRAY[2,3]) {1,2,3} array_remove array_remove ( anycompatiblearray, anycompatible ) anycompatiblearray Removes all elements equal to the given value from the array. The array must be one-dimensional. Comparisons are done using IS NOT DISTINCT FROM semantics, so it is possible to remove NULLs. array_remove(ARRAY[1,2,3,2], 2) {1,3} array_replace array_replace ( anycompatiblearray, anycompatible, anycompatible ) anycompatiblearray Replaces each array element equal to the second argument with the third argument. array_replace(ARRAY[1,2,5,4], 5, 3) {1,2,3,4} array_reverse array_reverse ( anyarray ) anyarray Reverses the first dimension of the array. array_reverse(ARRAY[[1,2],[3,4],[5,6]]) {{5,6},{3,4},{1,2}} array_sample array_sample ( array anyarray, n integer ) anyarray Returns an array of n items randomly selected from array. n may not exceed the length of array's first dimension. If array is multi-dimensional, an item is a slice having a given first subscript. array_sample(ARRAY[1,2,3,4,5,6], 3) {2,6,1} array_sample(ARRAY[[1,2],[3,4],[5,6]], 2) {{5,6},{1,2}} array_shuffle array_shuffle ( anyarray ) anyarray Randomly shuffles the first dimension of the array. array_shuffle(ARRAY[[1,2],[3,4],[5,6]]) {{5,6},{1,2},{3,4}} array_sort array_sort ( array anyarray , descending boolean , nulls_first boolean ) anyarray Sorts the first dimension of the array. The sort order is determined by the default sort ordering of the array's element type; however, if the element type is collatable, the collation to use can be specified by adding a COLLATE clause to the array argument. If descending is true then sort in descending order, otherwise ascending order. If omitted, the default is ascending order. If nulls_first is true then nulls appear before non-null values, otherwise nulls appear after non-null values. If omitted, nulls_first is taken to have the same value as descending. array_sort(ARRAY[[2,4],[2,1],[6,5]]) {{2,1},{2,4},{6,5}} array_to_string array_to_string ( array anyarray, delimiter text , null_string text ) text Converts each array element to its text representation, and concatenates those separated by the delimiter string. If null_string is given and is not NULL, then NULL array entries are represented by that string; otherwise, they are omitted. See also string_to_array. array_to_string(ARRAY[1, 2, 3, NULL, 5], ',', '*') 1,2,3,*,5 array_upper array_upper ( anyarray, integer ) integer Returns the upper bound of the requested array dimension. array_upper(ARRAY[1,8,3,7], 1) 4 cardinality cardinality ( anyarray ) integer Returns the total number of elements in the array, or 0 if the array is empty. cardinality(ARRAY[[1,2],[3,4]]) 4 trim_array trim_array ( array anyarray, n integer ) anyarray Trims an array by removing the last n elements. If the array is multidimensional, only the first dimension is trimmed. trim_array(ARRAY[1,2,3,4,5,6], 2) {1,2,3,4} unnest unnest ( anyarray ) setof anyelement Expands an array into a set of rows. The array's elements are read out in storage order. unnest(ARRAY[1,2]) 1 2 unnest(ARRAY[['foo','bar'],['baz','quux']]) foo bar baz quux unnest ( anyarray, anyarray , ... ) setof anyelement, anyelement [, ... ] Expands multiple arrays (possibly of different data types) into a set of rows. If the arrays are not all the same length then the shorter ones are padded with NULLs. This form is only allowed in a query's FROM clause; see . select * from unnest(ARRAY[1,2], ARRAY['foo','bar','baz']) as x(a,b) a | b ---+----- 1 | foo 2 | bar | baz See also about the aggregate function array_agg for use with arrays.