What is the purpose of using SQL aggregate functions?

The purpose of using SQL aggregate functions is to perform calculations on a set of values. Aggregate functions allow you to summarize large quantities of data by returning a single value based on a group of values from a database column. Common aggregate functions include COUNT, SUM, AVG, MIN, and MAX. For instance, if you need to calculate the total sales from all transactions in a sales table, you would use the SUM aggregate function to add up all the sales figures. This ability to compute a single summary result from multiple rows is fundamental in SQL for generating reports and performing data analysis, making it a critical skill for data manipulation and interpretation.

The other options describe functionalities that are not the primary purpose of aggregate functions. Manipulating text strings pertains to string functions, creating user-defined functions is related to custom function creation, and enforcing data integrity deals with constraints and rules in a database, none of which directly align with the role of aggregate functions.