Database

Think about searching for a contact in your phone. You can either scroll through everything or jump straight to a specific letter. That’s basically the difference between regular database access and using covering indexes in SQL. They can make your queries run way faster, but many developers don’t know about them or use them properly. Let’s talk about what they are and when you should use them. What is a Covering Index? A covering index is simply an index that has all the columns your query needs, so the database doesn’t have to go back to the actual table. W ...

I’ve been writing SQL for years, and one thing I’ve noticed is how many developers stick with subqueries for everything. But Common Table Expressions (CTEs) can often make your code much cleaner and sometimes faster too. Let me show you when you might want to reach for a CTE instead. Understanding the Basics So what’s the difference? A subquery is just a query nested inside another query (query-ception, if you will), while a CTE is more like a temporary named result that you can reference in your main query. CTEs only stick around for the statement they’re in. ...

Let’s talk about two SQL operators I use all the time: EXISTS and IN. Both help filter records with subqueries, but they work quite differently behind the scenes. Getting this right can make your queries run much faster. How EXISTS and IN Work In simple terms, EXISTS checks if any matching rows exist, while IN compares a value to a list of results. Here’s what they look like in action: ...