Imagine we want to create a promotional message that includes both a product’s name (formatted in uppercase) and the month name of its most recent order date. We might need to combine string functions like UPPER or SUBSTRING along with date functions like MONTHNAME. Nesting these functions lets us produce a single, clean result in just one query.

By learning to nest functions, we open the door to building powerful, concise queries that perform multiple transformations at once. Our main goal is to:

  • Understand what nesting functions means in SQL.

  • Recognize when and why we might combine multiple SQL functions in a single query.

  • Learn best practices for writing nested function queries clearly and effectively.

What is nesting functions and why it matters

Nesting functions means using one function’s output as the input to another function in a single SQL statement. This is incredibly helpful when we have to perform multiple operations on the same data. For instance, we might want to:

  • Convert a string to uppercase.

  • Extract a specific portion of that string.

  • Combine it with date information in one go.

  • Minimize the need for intermediate steps or temporary tables.

  • Make code more concise and expressive.

Nesting also makes our queries more readable when used with good formatting and clear intention.

Combining multiple functions in a single query

When we combine multiple functions, we perform them in a carefully arranged sequence. The result of an inner function immediately becomes the input of the outer function. For example, using the UPPER function on the result of a SUBSTRING call applies uppercase formatting specifically to the extracted portion of the string.

Consider a scenario where we want to see the month name using MONTHNAME and year using YEAR of each order date, along with the first three letters of the corresponding customer’s name in uppercase using UPPER and SUBSTRING. We can achieve this as follows:

Get hands-on with 1400+ tech skills courses.