Impress Your Coworkers by Using SQL UNPIVOT!

This is a nice guide on Pivot and UnPivot usage for real problems:

 
I’ve recently encountered a very interesting question on Stack Overflow by an unnamed user. The question was about generating a table of the following form in Oracle, using a table valued function:

Description   COUNT
-------------------
TEST1         10
TEST2         15
TEST3         25
TEST4         50

The logic that should be implemented for the COUNT column is the following:

• TEST1: count of employees whose sal < 10000
• TEST2: count of employees whose dept > 10
• TEST3: count of employees whose hiredate > (SYSDATE-60)
• TEST4: count of employees whose grade = 1

Challenge accepted!
 
Source: Impress Your Coworkers by Using SQL UNPIVOT!