Unnesting Lists & Structs with DuckDB’s UNNEST() Function

DuckDB has an unnest() function that we can use to unnest lists and structs. Well, it can also be applied to NULL, but that’ll return an empty result.

By “unnest” I mean it takes the list or struct, and it returns its contents as rows in a table. You might say that it converts lists and structs into tables, where each item in the list or struct becomes a row in the table.

Below are examples of using DuckDB’s unnest() function to unnest lists and structs.

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Check if a Sub-List Appears in a Larger List in DuckDB: LIST_HAS_ALL()

When working with lists in DuckDB, we sometimes need to check whether a list contains specific elements. The list_has_all() function is a handy tool that allows us to verify if all elements of one list exist within another. This function is particularly useful in filtering queries, data validation, and advanced list-based operations.

In this article, we’ll explore how list_has_all() works in DuckDB.

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Flattening Nested Lists with DuckDB’s FLATTEN() Function

DuckDB has a flatten() function that we can use to flatten nested lists. The function concatenates a list of lists into a single list. So whether the outer list contains just one list or multiple lists, we can use the flatten() function to flatten them into one list.

However, it only goes one level deep, so that’s something to keep in mind.

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5 Functions that Concatenate Lists in DuckDB

DuckDB provides us with a bunch of list concatenation functions that do exactly the same thing; concatenate two lists. Actually, they’re all synonyms and so they can all be used interchangeably. There’s also a more general concatenation function that can also be used on lists.

So this article presents five functions that we can use to concatenate lists.

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