SQL Server Database Administrator Question:
Download Questions PDF

What's the difference between a primary key and a unique key?

Answer:

Both primary key and unique enforce uniqueness of the column on which they are defined. But by default primary key creates a clustered index on the column, where are unique creates a nonclustered index by default. Another major difference is that, primary key doesn't allow NULLs, but unique key allows one NULL only.

Download SQL Server DB Administrator Interview Questions And Answers PDF

Previous QuestionNext Question
If you encounter this kind of an error message, what you need to look into to solve this problem?What are cursors?
Explain different types of cursors?
What are the disadvantages of cursors?
How to avoid cursors?