Structured Query Language (SQL) is a powerful tool for managing and manipulating relational databases. When working with databases, it's common to encounter situations where you need to retrieve ...

Imagine you’re a librarian, and someone asks you, “How many different genres of books do you have?” Would you count every book on the shelf? Of course not! You’d just list the unique genres. That’s ...

Compares the equality of two expressions and guarantees a true or false result, even if one or both operands are NULL. Any valid expression. The expression can be a column, a constant, a function, a ...

This function returns the approximate number of unique non-null values in a group. :::image type="icon" source="../../includes/media/topic-link-icon.svg" border ...