Improve company productivity with a Business Account.Sign Up

x
?
Solved

Cluster, non-cluster index, pk, unique...

Posted on 2014-12-21
2
Medium Priority
?
113 Views
Last Modified: 2014-12-31
At 7:11 min. into this video, at the screenshot below, the explanation is about having cluster, non-cluster index, pk, unique:

https://www.youtube.com/watch?v=ITcOiLSfVJQ

Question: Could you please expand on this discussion and also explain why database safety issue raised here?

index
0
Comment
Question by:Mike Eghtebas
2 Comments
 
LVL 38

Assisted Solution

by:ste5an
ste5an earned 600 total points
ID: 40512026
Imho "saftey" refers to carelessness when creating indices. So a primary key is per default a clustered index in shortened syntax.

See Heaps.
In most cases it's better to have a clustered index on the primary key, cause when it's used in foreign key relations it may avoid additional sorting.

But that's just a guess.
0
 
LVL 54

Accepted Solution

by:
Vitor Montalvão earned 1400 total points
ID: 40513005
Only if safety means a way to guarantee the uniqueness of a row (no duplicate rows).
The examples shows the different ways to do that, either using PK (always Unique but can be Clustered or non-clustered) or creating indexes with Unique Constraints (can be also Clustered or non-clustered).
Remember that you can only have one clustered index by table because it's the index that says how your records will be physically ordered.
0

Featured Post

Free Tool: Site Down Detector

Helpful to verify reports of your own downtime, or to double check a downed website you are trying to access.

One of a set of tools we are providing to everyone as a way of saying thank you for being a part of the community.

Question has a verified solution.

Are you are experiencing a similar issue? Get a personalized answer when you ask a related question.

Have a better answer? Share it in a comment.

Join & Write a Comment

In part one, we reviewed the prerequisites required for installing SQL Server vNext. In this part we will explore how to install Microsoft's SQL Server on Ubuntu 16.04.
During the weekend, I was asked to investigate into a deadlock in SQL Server 2014. SQL being something I don’t really fancy myself being an expert at, I had to do some refreshing. This article is a collection of my notes.
Via a live example, show how to set up a backup for SQL Server using a Maintenance Plan and how to schedule the job into SQL Server Agent.
Using examples as well as descriptions, and references to Books Online, show the documentation available for datatypes, explain the available data types and show how data can be passed into and out of variables.

588 members asked questions and received personalized solutions in the past 7 days.

Join the community of 500,000 technology professionals and ask your questions.

Join & Ask a Question