What are the functions of “group by” in SQL?

In SQL, the GROUP BY statement is used to group query results by one or more columns, allowing for aggregate operations to be performed on each group. The functions of GROUP BY include:

1. Group the query results by the specified column.
2. Perform aggregation operations on each group, such as calculating the sum, average, maximum, minimum, etc.
3. Aggregate functions (such as SUM, AVG, MAX, MIN, COUNT) can be used to calculate values for each group.
4. You can filter groups using the HAVING clause (similar to the WHERE clause).
5. Multiple columns can be used to group data, in order to achieve multi-level grouping.
6. The result set of groups is sorted in ascending order based on the grouping column.

In conclusion, the purpose of GROUP BY is to group the query results based on a specified column and perform aggregate functions on each group, resulting in more specific and meaningful data analysis outcomes.