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    MaxCompute:FLATTEN

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    MaxCompute:FLATTEN

    Last Updated:Mar 25, 2026

    Converts an ARRAY<ARRAY<T>> into a single ARRAY<T> by concatenating the elements of each sub-array in order.

    Syntax

    flatten(arrayOfArray)

    Parameter

    Parameter Type Description
    arrayOfArray ARRAY<ARRAY<T>> An array whose elements are arrays. If the input parameters are not arrays of the ARRAY data type, an error is returned.

    Return value

    Returns an ARRAY<T> containing the concatenated elements of all sub-arrays, in order.

    • If arrayOfArray is null, returns null.

    • If the input parameters are not arrays of the ARRAY data type, an error is returned.

    Examples

    Flatten an array of arrays

    SELECT flatten(array(array(1, 2), array(3, 4)));

    Result:

    [1, 2, 3, 4]

    Return null when the input is null

    SELECT flatten(null);

    Result:

    NULL

    Related functions

    FLATTEN is a complex type function. For more information about functions used to process ARRAY, MAP, STRUCT, and JSON data, see Complex type functions.