Solved

multiple unique columns in a table

Posted on 2011-09-16
8
387 Views
Last Modified: 2012-05-12
can we have multiple unique columns in a table. I was not clear on this concept. Please advise. thanks in advance
0
Comment
Question by:gudii9
[X]
Welcome to Experts Exchange

Add your voice to the tech community where 5M+ people just like you are talking about what matters.

  • Help others & share knowledge
  • Earn cash & points
  • Learn & ask questions
8 Comments
 
LVL 47

Expert Comment

by:for_yan
ID: 36552810
you can have multiple unique columns in a table - there is nothing that may prevent it
0
 
LVL 47

Accepted Solution

by:
for_yan earned 125 total points
ID: 36552821
Let's say you have the table of patients of the hospital - they may have their own id for each patient , but they may have a column for insusrance id and those
may be also be unique - certainly no problem with that
0
 
LVL 37

Assisted Solution

by:momi_sabag
momi_sabag earned 125 total points
ID: 36552830
you can have as many unique constraint you want on a table
a unique constraint verify that a column or set of columns have unique values in every row in a table
0
Transaction Monitoring Vs. Real User Monitoring

Synthetic Transaction Monitoring Vs. Real User Monitoring: When To Use Each Approach? In this article, we will discuss two major monitoring approaches: Synthetic Transaction and Real User Monitoring.

 
LVL 21

Assisted Solution

by:Amitkumar Panchal
Amitkumar Panchal earned 125 total points
ID: 36553738
Yes, You can have unique constraint on the all fields of the table. Only thing is that if the column having unique constraint must contains a unique value in that field across the table. However, the field contains a null (no value) value in it, so multiple null values are allowed in the field having a  unique constraint.
0
 
LVL 45

Assisted Solution

by:Kent Olsen
Kent Olsen earned 125 total points
ID: 36553894
Hi gudi,

The easiest way to enforce multiple unique columns in a table is to put a unique index on each of the columns.  

In fact, if you have a significant amount of data in the table it will be almost imperative to have these columns indexed as every insert or update will need to verify that the new data is unique within the column.  Without indexes on these column a full table scan will be required just to insert a new row!


Good Luck,
Kent
0
 
LVL 7

Author Comment

by:gudii9
ID: 36718886
How to put  unique index on each column
0
 
LVL 47

Expert Comment

by:for_yan
ID: 36718899
you can create index for any column or you can impose unique constraint on each colimn -
thes are different things
0
 
LVL 45

Expert Comment

by:Kent Olsen
ID: 36718913
Hi gudi,

You'll need to add the index or constraint for each column that must be unique.

CREATE UNIQUE INDEX idx0001 ON mytable (column1);
CREATE UNIQUE INDEX idx0002 ON mytable (column2);
etc....



Kent
0

Featured Post

Get 15 Days FREE Full-Featured Trial

Benefit from a mission critical IT monitoring with Monitis Premium or get it FREE for your entry level monitoring needs.
-Over 200,000 users
-More than 300,000 websites monitored
-Used in 197 countries
-Recommended by 98% of users

Question has a verified solution.

If you are experiencing a similar issue, please ask a related question

How to Unravel a Tricky Query Introduction If you browse through the Oracle zones or any of the other database-related zones you'll come across some complicated solutions and sometimes you'll just have to wonder how anyone came up with them.  …
Shell script to create broker configuration file using current broker Configuration, solely for purpose of backup on Linux. Script may need to be modified depending on OS-installation. Please deploy and verify the script in a test environment.
This video teaches viewers about errors in exception handling.
This tutorial explains how to use the VisualVM tool for the Java platform application. This video goes into detail on the Threads, Sampler, and Profiler tabs.

724 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