PostgreSQL: Multiple GROUP BY using GROUPING SETS in Single SQL Query

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In this post, I am sharing one demonstration of PostgreSQL GROUPING SETS.
This is very useful for PostgreSQL Database Developers who require to perform multiple GROUP BY in one single query.

Now take one example, you want to find the count of Employee based on two columns: Employee Department , Employee Joining Year.
For this query, you have to write different two queries and If you want to combine results of both the query, you should use UNION clause.

But using GROUPING SETS, we can prepare this result into one single query.

Below is a full demonstration of this:

Create a table with Sample data:

Count of Employee, Group By Department column:

Count of Employee, Group By Joining Year:

GROUP BY above two queries using GROUPING SETS:

The Result: