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groupArray

Syntax: groupArray(x) or groupArray(max_size)(x)

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.

Example

SELECT * FROM default.ck;

┌─id─┬─name─────┐
│ 1 │ zhangsan │
│ 1 │ ᴺᵁᴸᴸ │
│ 1 │ lisi │
│ 2 │ wangwu │
└────┴──────────┘

Query:

select id, groupArray(10)(name) from default.ck group by id;

Result:

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

The groupArray function will remove ᴺᵁᴸᴸ value based on the above results.

  • Alias: array_agg.