String Aggregation — Solution & ExplanationProblems / String Aggregation / EditorialApproachSQLSTRING_AGG(employee_name, ', ' ORDER BY employee_name) concatenates values with a delimiter. The ORDER BY inside the function controls the order of concatenation.PySpark

F.collect_list("employee_name") — gathers all names into an array.

F.sort_array(...) — sorts the array alphabetically.

F.concat_ws(", ", ...) — joins array elements with a delimiter.

Key ConceptString aggregation is essential for denormalizing data — e.g., showing all tags for a product or all skills for a user in a single row.Hints

DuckDB supports STRING_AGG(column, separator ORDER BY column) for ordered concatenation.

In PySpark, collect_list gathers values into an array, sort_array sorts it, and concat_ws joins them.

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