Compare to previous record

[shauns1]

Hi

What is the correct way to compare a new record with the one before it. Basically, I have a table that stores web page names. Before adding another page name to the table, I want to check that the last one entered isn't the same page. If it is, the page name doesn't get entered again.

Is there a simple SQL trick for this?

Many thanks

Shaun

 

[ca8msm]

Can you set the page name to be a primary key?


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[shauns1]

Hi, thanks for responding.

Not really because the same page name will appear multiple times - I just don't want it inserted twice in a row, oif that makes sense...

 

[ca8msm]

Oh, so you don't want it to appear if the previous row has had it entered? In that case you'll have to have a way of identifying what the last row actually is. Do you have a timestamp field that could be used to determine the latest row?


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[fredericofonseca]

Timestamp is not advisable for this situation, as you may have several records with the same timestamp if you have a fast enough machine, and you would then be unable to know for sure which record was the last one added.



The only way I see for that then is to have the following

1- Sequence number (either autonumber or programatically created)

2- (Before) insert trigger

On this trigger you issue a select of the entry where the sequence number precedes the one you are adding. then compare required fields and abort insert if required.



Regards

Frederico Fonseca
SysSoft Integrated Ltd

http://www.syssoft-int.com

 

[shauns1]

Yes, exactly! I do have an autonumber field and that is exactly the question I am asking.

How do I make a Before Insert trigger and how do a find out what the preceeding number is?

Many thanks

Shaun