What is the difference between SQL aggregate functions and window functions?

What is the difference between SQL aggregate functions and window functions?

SQL aggregate functions perform calculations on a set of values and return a single value, while window functions perform calculations across a set of rows related to the current row, returning a value for each row.

Can you give me examples of both types of functions?

Sure! An example of an aggregate function is SUM(), which adds up values in a column. A window function example is ROW_NUMBER(), which assigns a unique number to each row within a partition.

When should I use window functions instead of aggregate functions?

Use window functions when you need to perform calculations across a set of rows while retaining the individual row data. Aggregate functions are best when you want a single summary value.

Are there any performance differences between them?

Yes, window functions can be more efficient in certain scenarios since they avoid the need for subqueries or additional joins that aggregate functions might require.