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I have a table that contains a master list of items and an associated table that contains a unique text string only on specific values (determined by the application that inserts the data).

Example: Master Table (Assets)

Asset_ID    IP Address           Operating System    Host Name
1           123.456.789.125      Windows             BobsComputer
2           987.654.321.126      Windows             TomsComputer
3           456.123.789.127      Windows             JennysComputer

The associated table Unique_ID looks like this, joined on the Asset_ID

Special_ID  Asset_ID    Unique_ID
1           1           xhsieriyfh0308487
2           3           098uindifnoei8384

What I am trying to get is a query that gives me a of all items both IN Unique_ID and NOT IN Unique_ID Essentially the output I'm looking for is:

With_Unique_ID      Without_Unique_ID
2                   1

I know it has something to do with making subqueries but I can't seem to find the right syntax/command order to make it work. It's if that makes a difference.

  • What does it mean to have a column "in unique_id"? define "item" (guessing asset in master table)? does "in unique_id" mean connected by way of asset? can you delete the columns you're not using, and perhaps give reasonable names (table is called "_id")? No reason to make things more complex than need be. – Evan Carroll Mar 26 '18 at 22:20
  • The Assets table has all the items in inventory. The Unique_ID field only contains a record associated with an asset if a specific flag (determined by the logic in the application) is true, so not every Asset has a record in the Unique_ID table. – Sean Mar 28 '18 at 14:53
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Something like this may be:

select count(u.asset_id) as with_unique_id,
       count(*) - count(u.asset_id) as without_unique_id
from assets a left join the_other_table u on a.asset_id = u.asset_id

(not tested)

2

You can use conditional aggregation with an outer join

select count(*) filter (where at.asset_id is not null) with_unique_id, 
       count(*) filter (where at.asset_id is null) as without_unique_id
from assets a
  left join associated_table at on at.asset_id = a.asset_id;
  • The issue with this is there isn't a null value in Unique_ID when the tables are joined, even with a left join. Honestly not sure why, even though I know there's supposed to be. But I know that if I run a test query that searches for NULL values after the join, nothing is returned. – Sean Mar 28 '18 at 14:50
  • @Sean: there will be a NULL value in asset_id due to the outer join – a_horse_with_no_name Mar 28 '18 at 14:55

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