groupArray

Introduced in: v1.1.0

Creates an array of argument values. Values can be added to the array in any (indeterminate) order.

The second version (with the max_size parameter) limits the size of the resulting array to max_size elements. For example, groupArray(1)(x) is equivalent to [any(x)].

In some cases, you can still rely on the order of execution. This applies to cases when SELECT comes from a subquery that uses ORDER BY if the subquery result is small enough.

The groupArray function will remove NULL values from the result.

Syntax

groupArray(x)
groupArray(max_size)(x)

Aliases: array_agg

Parameters

max_size — Optional. Limits the size of the resulting array to max_size elements. UInt64

Arguments

x — Argument values to collect into an array. Any

Returned value

Returns an array of argument values. Array

Examples

Basic usage

CREATE TABLE ck (id UInt8, name String) ENGINE = Memory;
INSERT INTO ck VALUES (1, 'zhangsan'), (1, 'lisi'), (2, 'wangwu');

SELECT id, groupArray(10)(name) FROM ck GROUP BY id ORDER BY id;

┌─id─┬─groupArray(10)(name)─┐
│  1 │ ['zhangsan','lisi']  │
│  2 │ ['wangwu']           │
└────┴──────────────────────┘