Question

So I have three tables I am trying to pull data from with the following query:

select tats.machine_interval_id as machine_interval_id,
       tats.interval_type as interval_type, 
       tats.interval_category as interval_category,
       ops.opstatemnemonic as operational_state, 
       nptc.categorytype as idle_category,
       tats.interval_duration as interval_duration
from temp_agg_time_summary tats
left outer join operationalstates ops on ops.opstateid=tats.operationalstatenumeric
left outer join nptcategories nptc on nptc.categoryid=tats.categorytypenumeric

The problem I’m having is that whenever there is a value that is not null from the nptcategories table, it double the record which in turns throws off any calculations I have later in my packages. I believe the problem has to do with having more than one left outer join in the query. My question may see fairly simple, but I’m new to PL/SQL so bear with me.

What I want to know is how can I use multiple left outer joins in a query with out having this problem occur? What would be a better way to structure this query?

Update

Okay so I found the offending line of code it is below:

left outer join nptcategories nptc on nptc.categoryid=tats.categorytypenumeric

Also when using distinct, it removes all of the duplicate records, but will using this cause any problems I am unaware of? Should I focus more on figuring out why the join above does not work properly, or is the distinct good enough?

Answer 1

Okay, so after taking Wolf’s suggestion, i went in and ran the following line of code

    select categorytype, count(*) 
from nptcategories 
group by categorytype 
having count(*) > 1;

After running this, i found that somehow there were duplicates of records in this table so, this was fixed by removing the duplicates and setting the table to have unique ids. This was done by using the following script on the DB:

alter table nptcategories add constraint nptcatidunq unique(categoryid)