Database Management Systems
If you’ve ever used list_concat() or any of its aliases to concatenate lists in DuckDB, you may have been disappointed to find out that it only concatenates two lists. Any more than two lists and it returns an error. At least that’s how it works at the time of this writing.
Fortunately, there are some alternatives we can use in order to concatenate three or more lists.
Here are four ways to concatenate three or more lists in DuckDB.
DuckDB has emerged as a powerful analytical database system designed for fast in-memory data processing. One common analytical task involves calculating time differences between events—whether measuring intervals between transactions, tracking service response times, or analyzing temporal patterns in time series data.
This article provides an exploration of calculating time differences in DuckDB, covering both basic and slightly more advanced techniques.
You may be aware that DuckDB includes a typeof() function that works just like the SQLite equivalent; it returns the data type of its argument. But did you know that DuckDB also provides us with a pg_typeof() function that does essentially the same thing?
So why would DuckDB need a pg_typeof() function that does basically the same thing as typeof()? Let’s find out!
DuckDB has a list_where() function that returns a list after a user-supplied mask has been applied. We pass the list as the first argument, and a list of Boolean values as the second. The list of Boolean values is applied as a mask to the list, which determines which values in the list are returned.
DuckDB provides us with a couple of easy ways to perform additions and subtractions on dates. In particular, we can use the - operator to do the job, or the date_add() operator combined with the - operator.
Here are two options for subtracting days from a date in DuckDB.
This article demonstrates how to output your DuckDB query results in TCL list format, which can be useful when integrating with TCL scripts or systems that expect TCL-formatted data.
DuckDB provides a few options for slicing lists, including the list_slice() function and its alias, array_slice(). We can also use bracket notation for a slightly more concise option. Bracket notation is where we append the slice details to the list.
Below are examples of using bracket notation to slice lists in DuckDB.
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.
When presented with a list of numbers, there are many things we might want to do with it. One is to get the average value of all values in the list. Fortunately DuckDB provides us with several ways to do this.
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.