DQL – Conversational SQL

Understanding and Handling NULL Values in SQL

When working with SQL, one of the most confusing concepts for beginners is dealing with NULL values. NULL doesn’t represent

In a previous post, we introduced window functions to add “group context” without collapsing rows. Now let’s build on that

In an earlier post we talked about summarizing data with GROUP BY and aggregate functions using calculations like COUNT(), SUM(),

SQL isn’t just about selecting and aggregating data—it can also apply conditional logic to transform or categorize results. That’s where

So far we’ve seen how GROUP BY can summarize data into meaningful results. But what if you need totals and

So far, we’ve learned how to read data with SELECT, filter rows with WHERE, and sort results with ORDER BY.

After learning how to retrieve data with SELECT and filter it with WHERE, the next step is organizing the results.

Once you know how to retrieve data with a SELECT statement, the next step is learning how to filter the

When starting a new SQL project, one of the first steps is exploring the data you already have. Understanding the