The COALESCE SQL query allows us to perform operations on NULL values. Here’s what it is, how it works, and why you need to pay attention to it.
Introduction
The SQL language is a beauty. It is a beauty not only because it’s the language we talk to many relational databases like MySQL, SQL Server, and PostgreSQL, but also because it has many caveats unique to itself. The COALESCE SQL query is one of those caveats.
What is the COALESCE SQL Query and When to Use It?
In simple words, this SQL query is a part of an SQL statement that returns the first value in a list that is not NULL. In other words, this SQL query would return “BreachDirectory.com” because it is the first non-null value in an array:
SELECT COALESCE(NULL, NULL, NULL, NULL, NULL, 'BreachDirectory.com', NULL, NULL, 'BreachDirectory');
The COALESCE SQL clause is just that – it isn’t a “tool” or a client of any sort: the SQL clause allows us to return the first item in an array of values that is not NULL. We use such a clause in a SQL query once we have an array of values and have a use case that necessitates the first non-NULL value to be retrieved, displayed, or otherwise acted on.
FAQ
What Does This SQL Query Do?
This SQL query allows us to return the first value in an array of values that is not NULL.
When to Use the COALESCE SQL Query?
Consider using the COALESCE SQL query when you have a use case that necessitates acting on an array of values and returning a value that isn’t NULL.