array_slice

Returns an array constructed from a specified subset of elements of the input array.

Syntax

array_slice( <array> , <start> , <end> , <step> )

Arguments

<array>

The source array of which a subset of the elements are used to construct the resulting array.

<start>

A position in the source array. The position of the first element is 0.

<end>

A position in the source array.

<step>

An iteration delta.

Returns

An ARRAY constructed from a specified subset. NULL if the input array is NULL.

Usage notes

Array slice returns a slice defined by the two slice parameters, <start> and <end>, and an iteration delta, <step>. Each of these parameters can be NULL.

The default value for <step> is 1. The default values for <start> and <end> depend on the sign of <step>:

Condition	start	end
step >= 0	0	len
step < 0	len-1	-len-1

The direction of the iteration is defined by the sign of step. If step is positive, the iteration is from <start> to <end>. If step is negative, the iteration is from <end> to <start>.

Examples

Here is a simple example:

SELECT ["a", "b", "c", "d", "e", "f", "g"] AS v
SELECT
    array_slice(v, 1, 3, NULL) AS s1,
    array_slice(v, 5, NULL, NULL) AS s2,
    array_slice(v, 1, 5, 2) AS s3,
    array_slice(v, 5, 1, -2) AS s4,
    array_slice(v, NULL, NULL, -1) AS s5;

+-----------+-----------+-----------+-----------+-------------------------------+
| s1        | s2        | s3        | s4        | s5                            |
+-----------+-----------+-----------+-----------+-------------------------------+
| ['b','c'] | ['f','g'] | ['b','d'] | ['f','d'] | ['g','f','e','d','c','b','a'] |
+-----------+-----------+-----------+-----------+-------------------------------+