What is the purpose of the OVER clause in SQL?

In SQL, the OVER function is used to group, sort, and calculate query results so that various analytic functions can be applied within the result set. It is commonly used in conjunction with window functions to provide advanced analysis and computational capabilities on the query results.

The OVER function can be used in the following scenarios:

1. Grouping calculation: By using the PARTITION BY clause, the query results can be divided into multiple groups and aggregate functions such as SUM, AVG, COUNT can be applied in each group.
2. Sorting: By using the ORDER BY clause, you can sort the query results.
3. Window functions: By using window functions, a specific function such as RANK, LEAD, LAG can be applied to each row in a query result set for analysis and calculation purposes.

By using the OVER function, various analytical functions can be applied in query results without the need for subqueries or joining operations, simplifying SQL query writing and providing advanced analysis and calculation capabilities.