Adding column to select statement brings in all historical data - sql-server

Question

Good evening all!
I'm running into a really odd issue that I'm having trouble understanding.
I have 3 tables (parts table, parts move history and a parts detail table).
What I'm trying to do is have the result set return lot#,part#,product description,quantity,part location, what's currently in inventory (versus full history) and who last moved the product.
Now, for the query. When I run the below query, I get a result set of 4,751 rows; which lines up perfectly with my expected results. However, when I try to add in the userid field, I then get a result set of 186,573. This large result set appears to pull in all historic data versus just matching the userid to the 4,751 rows I actually need.
From the Parts Table I need (prod_desc)
From the Parts Detail Table I need (lot,part#,lotquantity,prtlocation)
From the Parts Move History Table I need (move_date,user_id)
4,751 Query:
SELECT DISTINCT
inv.lot,
inv.part#,
prt.prod_desc,
inv.lotquantity,
inv.prtlocation,
MAX(mv.move_date)AS 'Move Date'
FROM invdet AS inv
LEFT JOIN movetable AS mv ON inv.part# = mv.part#
LEFT JOIN partmstr AS prt ON inv.part# = prt.part#
WHERE inv.lot IS NOT NULL
GROUP BY inv.lot,inv.part#,prt.prod_desc,inv.lotquantity,inv.prtlocation
ORDER BY inv.prtlocation
186,573 Query:
SELECT DISTINCT
inv.lot,
inv.part#,
prt.prod_desc,
inv.lotquantity,
inv.prtlocation,
MAX(mv.move_date)AS 'Move Date'
mv.user_id
FROM invdet AS inv
LEFT JOIN movetable AS mv ON inv.part# = mv.part#
LEFT JOIN partmstr AS prt ON inv.part# = prt.part#
WHERE inv.lot IS NOT NULL
GROUP BY inv.lot,inv.part#,prt.prod_desc,inv.lotquantity,inv.prtlocation,mv.user_id
ORDER BY inv.prtlocation
If I don't use the MAX function, I do not get current inventory and instead get all results in the table, which I do not need. I'm still learning and my GROUP BY's leave a lot to be desired as I'm still wrapping my head around it (open to suggestions!). I'm sure there's a subquery I can throw in here somewhere, but I'm still figuring those out as well. Any help is greatly appreciated!

Answer 1

I think the problem is that when you insert mv.user_id from table movetable you get all part's movements and not only the last one with date max(mv.move_date).
One way is to remove the left join to movetable and use maybe a cross apply like
SELECT inv.lot,inv.part,prt.prod_desc,inv.lotquantity,inv.prtlocation,x.move_date,x.user_id
FROM invdet AS inv
CROSS APPLY(SELECT TOP 1
mv.user_id,mv.move_date
FROM movetable mv
WHERE inv.part=mv.part
ORDER BY mv.move_date DESC) AS x
LEFT JOIN partmstr AS prt ON inv.part=prt.part
WHERE inv.lot IS NOT NULL
ORDER BY inv.prtlocation
I've not tested it but should be fine, maybe a bit slow because cross apply executes one subquery per each row in inv table. If it is too slow, you can user ROWNUMBER to create a table composed of only the last movements and then use it in the LEFT JOIN, as follows
SELECT inv.lot,inv.part,prt.prod_desc,inv.lotquantity,inv.prtlocation,y.move_date,y.user_id
FROM invdet AS inv
LEFT JOIN(SELECT x.user_id,x.move_date,x.part
FROM (SELECT mv.user_id,mv.move_date,mv.part,rn=ROWNUMBER() OVER(PARTITION BY mv.part ORDER BY mv.move_date DESC)
FROM movetable mv) AS x
WHERE x.rn=1) AS y ON y.part=inv.part
LEFT JOIN partmstr AS prt ON inv.part=prt.part
WHERE inv.lot IS NOT NULL
ORDER BY inv.prtlocation
Hope it helps.