Thanks for posting. It will be easy for me to learn, if you give some example for invalid queries for the first point under important points.

Thanks Steve for the good question on new year.

Happy new year for everyone...

Thanks Mr.Bhuvnesh. Now i have created an index

CREATE INDEX IX_tmpsize_tmpsizepk

ON tmpsize (tmpsizepk);

Again the count of Extent remains same as before.

Trace will show the duration in milliseconds. Correct answer should be third option. Please check it out

Is there any performance difference in the below given three queries.

Note: Col1 is NOT NULL column

SELECT COUNT(*) FROM Sales.SalesOrderDetail;

SELECT COUNT(Col1) FROM Sales.SalesOrderDetail;

SELECT COUNT(0) FROM Sales.SalesOrderDetail;

Good question. Small trick cost 1 point

How to deallocate the unused pages?