PostgreSQL 18 reference · Array Functions

PostgreSQL ARRAY_LENGTH() Function

Return the length of one dimension of an array (use 1 for ordinary arrays). Empty arrays give NULL, not 0.

PostgreSQL 18

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Syntax

array_length(array, dimension)

Parameter	Description
`array`	An array value.
`dimension`	Which dimension, usually 1.

integer, or NULL for an empty array.

Length

SELECT array_length(ARRAY[10, 20, 30], 1) AS len, array_length('{}'::int[], 1) AS empty;

Output

 len | empty
-----+-------
   3 |  NULL
(1 row)

Run this on your computer — see “Get Started” for setup.

cardinality() gives 0 for empty arrays

SELECT cardinality(ARRAY[10, 20, 30]) AS n, cardinality('{}'::int[]) AS empty;

Output

 n | empty
---+-------
 3 |     0
(1 row)

Run this on your computer — see “Get Started” for setup.

CARDINALITY() · Return the total number of elements in an array across all dimensions, and 0 for an empty array.
UNNEST() · Expand an array into a set of rows, one per element. With several arrays it zips them into columns.
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