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    MaxCompute:ARRAY_JOIN

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    MaxCompute:ARRAY_JOIN

    Last Updated:Mar 26, 2026

    Concatenates the elements of an array into a string using a specified delimiter.

    Syntax

    array_join(array<T> <a>, <delimiter>[, <nullreplacement>]) → STRING

    Parameters

    Parameter Required Type Description
    a Yes array\<T\> The array to concatenate. T specifies the element data type. If elements are not of the STRING type, MaxCompute converts them to STRING automatically.
    delimiter Yes STRING The string used to separate elements in the result.
    nullreplacement No STRING The string used to replace null elements.

    Usage notes

    • If the array contains null elements and nullreplacement is set, each null element is replaced with the value of nullreplacement.

    • If the array contains null elements and nullreplacement is not set, null elements are ignored.

    Examples

    Basic usage — join numeric elements with a comma delimiter:

    SELECT array_join(array(10, 20, 20, null, null, 30), ",");
-- 10,20,20,30

    With null replacement — replace each null element with the string "null":

    SELECT array_join(array(10, 20, 20, null, null, 30), "##", "null");
-- 10##20##20##null##null##30

    Related functions

    ARRAY_JOIN is a complex type function. For more information about functions that process complex type data such as ARRAY, MAP, STRUCT, and JSON, see Complex type functions.