DuckDB’s LIMIT and SAMPLE clauses both allow users to work with subsets of data, but they serve fundamentally different purposes and operate on different principles. While LIMIT returns a fixed number of rows from the beginning of a result set, SAMPLE provides a random sample from the dataset.
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Get the Last Day of the Month in DuckDB with LAST_DAY()
DuckDB provides us with a good selection of functions for working with date and timestamp values. One such function is the LAST_DAY() function, which returns the last day of the month of the given date.
The way it works is, we pass a date to the function, and it returns the date of the last day of that month.
Using LIST_RESIZE() to Resize a List in DuckDB
DuckDB provides us with a list_resize() function for those occasions where we need to resize a list. It also offers an alias called array_resize() that does exactly the same thing. When we resize a list using these functions, we specify how big we want the resulting list to be, and we can also specify a value to use for any extra elements that are added to the list.
A Quick Look at the REPEAT() Function in DuckDB
DuckDB has a repeat() function that enables us to output a repeating value easily and concisely. The way it works is that we pass the value to the function, followed by how many times we want it to be repeated. It returns that value repeated the specified number of times.
Detect Infinite Values in DuckDB with the ISINF() Function
In DuckDB, we can use the ISINF() function to check whether a value is finite. DuckDB supports infinite values, and so this function allows us to check for that. This can be useful when working with floating-point data that might contain special values like NaN (Not a Number) or infinity. The function also works on date and timestamp values, as they can be infinite too.
Using JSON_CONTAINS() in DuckDB to Check if a Value Exists in a JSON Document
In DuckDB, we can use the json_contains() function to check whether a specified JSON value is contained within another JSON structure. It returns a boolean (TRUE or FALSE) that indicates whether or not the value was found. We can also check for key value pairs, or even a full JSON object within the JSON document.
Understanding DuckDB’s ARG_MIN_NULL() Function
DuckDB has a arg_min_null() function that works in a similar way to the arg_min() function. That is, it finds the row with the minimum value in one column and returns the corresponding value from another column at that row.
But there’s also a difference between these two functions. The main difference is in the way they deal with NULL values. Also, arg_min_null() only accepts two arguments, whereas arg_min() accepts an optional third argument. Additionally, there aren’t any aliases for arg_min_null() at the time of writing (arg_min() has a couple of aliases).
In this article we’ll look at how arg_min_null() works, and we’ll compare it with arg_min() to see how each function handles NULL values.
LIST_REVERSE() vs LIST_REVERSE_SORT() in DuckDB: What’s the Difference?
DuckDB has a good range of functions for dealing with lists and arrays. Amongst these are list_reverse() and a list_reverse_sort(). Looking at their names, you could be forgiven for thinking that these do the same thing. But they don’t.
If you’re wondering why DuckDB has a list_reverse() and a list_reverse_sort() function, read on.
Convert Column Values to a JSON Array with DuckDB’s JSON_GROUP_ARRAY() Function
The json_group_array() function in DuckDB is used to aggregate values into a JSON array, making it especially useful when working with structured or semi-structured data such as JSON. This function is part of DuckDB’s JSON extension and works similarly to DuckDB’s string_agg() or the group_concat() function in some other RDBMSs, but instead of returning a delimited string, it returns a well-formed JSON array.
This function is particularly helpful when we need to represent grouped or hierarchical data in a JSON format for export, reporting, or further transformation.
An Overview of the TODAY() Function in DuckDB
DuckDB has a today() function that returns the current date. It’s similar to the current_date function, which does the same thing.
Here, we’ll look at how the today() function works, along with some basic examples.