Question: When we drop clustered index on the column, does it automatically drop primary key on the same column (if created)?
Does Dropping Primary Key Drop Clustered Index on the Same Column? – Interview Question of the Week #082
Question: When we drop primary key on the column, does it automatically drop a clustered index on the same column (if created)?
Answer: This is one of the most popular questions, whenever I ask this to any candidate, they usually give an answer in yes or no. However, if I ask them follow up question to confirm, I have noticed most of the time they change the reply or accept that they really do not know the answer. It is totally fine. As when I was beginning with SQL, I even did not know the answer of it. I learn doing various experiments and doing various interviews.
This is a very interesting question. I really do not know why interviews are fascinated with this question. One of the professional services I offer is to help organizations select an ideal employee for their organization and last week, I was on a conference call with a large MNC who was looking for performance tuning expert for their organization. We interviewed around 50 different employees and offered jobs to 2 experts and 1 has so far accepted it. One of the questions which I see my friends from the interview panel asking again and again was about Primary Key. I noticed that most of the candidate got it correct.
I am an independent database consultant and I focus on SQL Server Performance Tuning. The other day when I was working with my customer on a large project on performance tuning, we noticed a table which had created performance issues and it contains a huge amount of NULL data. In this blog post we will learn about NOT NULL constraint.
Question: Can Primary Key on any table contain NULL values? Why? Answer: Primary key on any table in SQL Server can not contain a null value.
Let us first see script which will return us tablename with schema where clustered index is not a primary key.
Question: How to Find Table Without Clustered Index (heap)?
Answer: In SQL Server, when we create a primary key it automatically creates clustered index on the table, unless we explicitly mentioned not to create one. Due to this reason, the most of the table where there is a primary key, there are good chances it is also a clustered index key.