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How can define a combination of rows as unique?

Posted: Tue Feb 13, 2007 12:57 am
by Betty_S
Hi

How can define a combination of rows as unique?

I'm using mysql and need to prevent duplicate row inserting. I don't want to define one column as unique but a combination of 3 columns.

How can I do that?

thanks

Posted: Tue Feb 13, 2007 2:21 am
by CoderGoblin
Primary keys are always defined as unique. I know in most databases you can define other columns as unique.

Code: Select all

alter table [table name] add unique ([column name]);
should work.

This is taken from www.pantz.org - Handy MySQL Commands

Posted: Tue Feb 13, 2007 4:20 am
by Mordred
CoderGoblin wrote:Primary keys are always defined as unique. I know in most databases you can define other columns as unique.

Code: Select all

alter table [table name] add unique ([column name]);
should work.

This is taken from www.pantz.org - Handy MySQL Commands
For multiple columns, it's

Code: Select all

alter table `table` add unique (`column1`, `column2`);
With phpMyAdmin it's called "Create an index on ... columns"

Posted: Tue Feb 13, 2007 10:20 am
by Kieran Huggins
That's a fine resource CoderGoblin -- thanks!

Posted: Tue Feb 13, 2007 6:30 pm
by RobertGonzalez
CoderGoblin - can you post that link in the Useful Resources thread?