Question

I’m trying to figure out how to write a script to select certain records/fields from one table, then join it to another table and include a column for a corresponding count. For example, this is what I have now:

select ID, Val from OriginalTable where Something = 1

Now I have another table which has records linking to this original table, where the a column OriginalID matches the ID of the OriginalTable. One example would be:

select * from OtherTable where OriginalID = 3

…where 3 = the ID of the OriginalTable.

What I’d like to do is add a column to the first statement which shows a count of the other table as shown in the second query. For example, this might be a result set:

ID    Val    Count
1     abc    15
2     def    23
3     ghi    42
4     jkl    19

How do I write this query to include this count?

Answer 1

There are a lot of ways to do this, but you could either use a Group By

select ID, Val, [Count] = count(1)
from OriginalTable be
left join OtherTable ot on be.OriginalID = ot.OriginalID
where Something = 1
group by ID,Val

or you could use OVER and Partition By:

select ID, Val, [Count] = count(1) OVER(PARTITION BY ID,Val)
from OriginalTable be
left join OtherTable ot on be.OriginalID = ot.OriginalID
where Something = 1

Personally I like the OVER method. There’s information on MSDN here.