DuckDB’s list_aggregate() function is a handy tool for performing grouped aggregations over lists. It allows us to apply any aggregate function (like sum, avg, min, max, count, etc.) to a list column as if each list item were a row.
The way it works is that we pass the list as the first argument, followed by the name of an aggregate function we want to apply to that list. The function will return its result as if it were the named aggregate function.
Continue readingMost SQL databases provide a cast() function and DuckDB is no exception. The purpose of the cast() function is to convert a value from one data type to another. This can also be referred to as casting the value as the other data type.
DuckDB has a list_slice() function that enables us to select multiple list items from a list, based on their index range within the list. For example, we can select all list items between position 5 and 10 in a list.
DuckDB’s epoch() function is a useful time conversion tool that allows us to transform timestamp values into Unix epoch time – the number of seconds that have elapsed since January 1, 1970 (UTC).
The function is particularly useful when working with time-series data and when we need to perform mathematical operations on timestamp values. By converting timestamps to integer representations, we can easily calculate time differences, group time-based data, or integrate with systems that use epoch time.
Continue readingDuckDB provides us with the list_has_any() function that enables us to find any overlapping elements across two lists. The way it works is that we pass two lists, and it returns true or false, depending on whether any element exists in both lists.
DuckDB has a list_zip() function that zips one or more lists to a new list with a length of the longest list provided. The new list contains unnamed structs of the elements from the original lists. We pass the lists to the function when we call it. We can also pass a Boolean value to specify whether or not to truncate all lists to the smallest list.
Below are some basic examples that demonstrate how the list_zip() function works.
Among DuckDB’s many tools for handling list data is the list_grade_up() function. This function works similarly to a sort operation, but instead of returning the sorted values themselves, it returns the indexes that represent the positions of those values in the original list.
Let’s take a quick look.
Continue readingIf you ever find yourself in the situation where you need to count up the number of unique elements in a list in DuckDB, you’ll be happy to know that there’s a list_unique() function that does exactly that.
DuckDB’s list_select() function allows us to extract specific elements from list columns based on their positions. This can be useful when we need to access or manipulate elements within arrays or lists.
While it’s true that DuckDB has a list_sort() function that allows us to sort lists, it’s also true that there’s a list_reverse_sort() function that sorts lists in reverse order.