ClickHouse/docs/en/sql-reference/aggregate-functions/reference/grouparraysample.md

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groupArraySample

Creates an array of sample argument values. The size of the resulting array is limited to max_size elements. Argument values are selected and added to the array randomly.

Syntax

groupArraySample(max_size[, seed])(x)

Arguments

• max_size — Maximum size of the resulting array. UInt64.
• seed — Seed for the random number generator. Optional. UInt64. Default value: 123456.
• x — Argument (column name or expression).

Returned values

• Array of randomly selected x arguments.

Type: Array.

Examples

Consider table colors:

┌─id─┬─color──┐
│  1 │ red    │
│  2 │ blue   │
│  3 │ green  │
│  4 │ white  │
│  5 │ orange │
└────┴────────┘

Query with column name as argument:

SELECT groupArraySample(3)(color) as newcolors FROM colors;

Result:

┌─newcolors──────────────────┐
│ ['white','blue','green']   │
└────────────────────────────┘

Query with column name and different seed:

SELECT groupArraySample(3, 987654321)(color) as newcolors FROM colors;

Result:

┌─newcolors──────────────────┐
│ ['red','orange','green']   │
└────────────────────────────┘

Query with expression as argument:

SELECT groupArraySample(3)(concat('light-', color)) as newcolors FROM colors;

Result:

┌─newcolors───────────────────────────────────┐
│ ['light-blue','light-orange','light-green'] │
└─────────────────────────────────────────────┘