Category: DuckDB

3 Easy Ways to Calculate the Median Value from a List in DuckDB

Posted on by Ian

While we might typically use DuckDB’s median() function to get the median value from a column, when it comes to getting the median value from a list, we need to modify this slightly. A list can contain many values, and so we need a way to calculate the median of all of those values, rather than a single value like we’d normally be doing when calculating the median value from a column.

Fortunately, DuckDB provides us with several easy options for achieving this. Below are three options for getting the median value from a list in DuckDB.

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How EPOCH_NS() Works in DuckDB

Posted on by Ian

DuckDB provides an epoch_ns() function that returns the Unix epoch time from a given date/time value in nanoseconds.

Unix epoch time is typically expressed as the number of seconds that have elapsed since January 1, 1970 (UTC), but it can also be expressed in other units, such as milliseconds, microseconds, and nanoseconds. DuckDB has specific functions for each of these units, with epoch_ns() being the function that returns it in nanoseconds.

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Using LIST_INTERSECT() to Extract Overlapping Elements from Two Lists in DuckDB

Posted on by Ian

The list_intersect() can be quite a handy function when working with lists in DuckDB. It accepts two lists as arguments, and it returns a list of elements that are common to both lists. It essentially performs a set intersection operation while preserving the list data type.

Duplicate values are ignored, so only one value is returned even if there are multiple occurrences in one or both lists.

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An Important Consideration When Choosing Between LIST_CONCAT() and || For Concatenating Lists in DuckDB

Posted on by Ian

When it comes to concatenating lists in DuckDB, we can use the list_concat() function (and its aliases), or the list concatenation operator (||). Often when we have a choice like this, we can use either option interchangeably. But that isn’t quite true in this case.

There’s an important difference between list_concat() and the || operator in DuckDB, and it all comes down to how it handles NULL values.

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A Quick Look at DuckDB’s JSON_VALUE() Function

Posted on by Ian

DuckDB provides a handful of functions for getting data from JSON documents. We can use them as long as the JSON extension is installed and loaded (which it is in most distributions). One such function for getting data from a JSON document is json_value(). This function extracts scalar data from the specified path in the JSON document. If the value isn’t scalar, then a NULL value is returned.

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Understanding JSON_EXTRACT_STRING() in DuckDB

Posted on by Ian

DuckDB has a json_extract_string() function that works similar to json_extract(), except that it returns its result as a string (varchar). The json_extract() function, on the other hand, returns its result as JSON.

The purpose of these two functions is to extract data from a JSON document. We’ll focus on the json_extract_string() function in this article.

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5 Functions that Return the Year from a Date in DuckDB

Posted on by Ian

When working with dates in DuckDB, some common tasks we might need to perform include extracting date parts from a date or timestamp value. For example we might want to extract the year from a date. Fortunately, DuckDB provides us with an abundance of options for doing that.

In this article, we’ll look at five different functions extract the year from a date in DuckDB.

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