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    PolarDB:Collection types

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    PolarDB:Collection types

    Last Updated:Jun 08, 2026

    PolarDB for Oracle supports three PL/SQL collection types: variable-size arrays (varrays), nested tables, and associative arrays. This page compares the three types and describes their limitations.

    Number of elements

    When a maximum element count is specified, that value is the upper bound for the collection. When no count is specified, the maximum is determined by the upper limit of the index type.

    Limitations

    • Associative array initialization constructors are not supported.

    • Construction forms for qualified expressions and iterator are not supported.

    • Multidimensional collection types are not supported. Multilevel nesting of collection types and record types is also not supported.

    • MULTISET-related operations are not supported.

    • When the DELETE collection method removes elements but retains their placeholders, avoid using the collection variable together with tables, as this will produce unexpected results.

    • IS [NOT] NULL can determine whether a collection variable is in the NULL state. Comparing collection variables with =, <, or > returns meaningless results.