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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Understanding EXTRACT() in DuckDB

DuckDB offers a variety of date functions, one of which is the extract() function. This function is designed to retrieve a specific date part from a date or timestamp value, and it can also be applied to intervals.

In this article, we’ll take a closer look at the extract() function and provide some straightforward examples to illustrate how it works.

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Fixing “Conversion Error” When Using COALESCE() in DuckDB

If you’re getting an error that reads “Conversion Error: Could not convert …etc” while using the COALESCE() function in DuckDB, it appears that you’re using arguments with incompatible types.

To fix this issue, try using CAST() or TRY_CAST() to ensure that all arguments are compatible. Alternatively, make sure the arguments to COALESCE() are of the same type (or at least, compatible types).

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Using TRY_STRPTIME() to Handle Errors When Constructing Timestamps in DuckDB

If you’ve ever used the strptime() function to create a timestamp in DuckDB, you may be aware that it will return an error if it can’t construct the timestamp from the format string/s provided.

While such an error could be useful in some situations, it could also be annoying in others.

Fortunately, DuckDB also provides the try_strptime() function, which will suppress any error that we might ordinarily get in such cases. This function returns null instead of an error.

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