Multiple Nested Inner Joins: not all records are shown - sql-server

Question

I have difficulty joining two tables that look like the following:
The main table PMEOBJECT which has a unique key named OBJECTID and
has in total 12768 rows.
Then I want to join PMEOBJECTVALIDITY on it which has an n:1 relationship with PMEOBJECT, since it has more rows,
because it saves the changes over time of PMEOBJECT (i.e. when a certain object is not
valid anymore), this one has 12789 rows (meaning only 21 objects
changed over time). However, I only want to have the current last
VALIDFROM date shown in the query. This all works fine.
Then the trouble starts when I want to join PMEOBJECTDIMENSION, which has an
n:1 relationship with PMEOBJECTVALIDITY and has 36737 rows in total.
SELECT
PMEOBJECT.OBJECTID
,PMEOBJECTVALIDITY.VALIDFROM
,PMEOBJECTDIMENSION.DIMENSION2_
FROM PMEOBJECT
LEFT JOIN PMEOBJECTVALIDITY
ON PMEOBJECTVALIDITY.OBJECTID = PMEOBJECT.OBJECTID
AND PMEOBJECTVALIDITY.DATAAREAID = PMEOBJECT.DATAAREAID
INNER JOIN(
SELECT
OBJECTID,
MAX(VALIDFROM) AS NEWFROMDATE,
MAX(VALIDTO) AS NEWTODATE
FROM PMEOBJECTVALIDITY B
GROUP BY OBJECTID
) B
ON PMEOBJECTVALIDITY.OBJECTID = B.OBJECTID
AND PMEOBJECTVALIDITY.VALIDFROM = B.NEWFROMDATE
LEFT JOIN PMEOBJECTDIMENSION
ON PMEOBJECTDIMENSION.OBJECTVALIDITYID = PMEOBJECTVALIDITY.RECID
AND PMEOBJECTDIMENSION.DATAAREAID = PMEOBJECTVALIDITY.DATAAREAID
INNER JOIN(
SELECT
OBJECTVALIDITYID,
MAX(VALIDFROM) AS NEWFROMDATE_2
FROM PMEOBJECTDIMENSION C
GROUP BY OBJECTVALIDITYID
) C
ON PMEOBJECTDIMENSION.OBJECTVALIDITYID = C.OBJECTVALIDITYID
AND PMEOBJECTDIMENSION.VALIDFROM = C.NEWFROMDATE_2
Results in query per step:
SELECT PMEOBJECT: 12768 rows
LEFT JOIN PMEVALIDITY: 12789 rows
INNER JOIN PMEVALIDITY: 12768 rows
LEFT JOIN PMEOBJECTDIMENSION: 36737 rows
INNER JOIN PMEOBJECTDIMENSION: 12729 rows
I want the end result again to have the same 12768 rows, I don't want any ObjectId to be left out.
What am I missing here?
Kind regards,
Igor

Answer 1

Following might help:
from PMEOBJECTDIMENSION onwards:
LEFT JOIN (SELECT PMEOBJECTDIMENSION.OBJECTVALIDITYID, PMEOBJECTDIMENSION.DATAAREAID
FROM PMEOBJECTDIMENSION
INNER JOIN(SELECT OBJECTVALIDITYID, MAX(VALIDFROM) AS NEWFROMDATE_2
FROM PMEOBJECTDIMENSION C
GROUP BY OBJECTVALIDITYID
) C
ON PMEOBJECTDIMENSION.OBJECTVALIDITYID = C.OBJECTVALIDITYID
AND PMEOBJECTDIMENSION.VALIDFROM = C.NEWFROMDATE_2
)X
ON X.OBJECTVALIDITYID = PMEOBJECTVALIDITY.RECID
AND X.DATAAREAID = PMEOBJECTVALIDITY.DATAAREAID
and select the distinct records if duplicates present.

Answer 2

The INNER JOINs are filtering out records- what you want is that the LEFT JOIN table (PMEOBJECTVALIDITY and PMEOBJECTDIMENSION) should only include records that have at least a match on the INNER JOIN queries (alias B and C). You can accomplish this with by nesting the INNER JOIN with the LEFT JOIN, generally done as follows:
SELECT *
FROM A
LEFT JOIN B
INNER JOIN C
ON B.ID = C.BID
ON A.ID = B.AID
Now B is INNER JOINed on C and will only contain records that have a match in C, but will preserve the LEFT JOIN not remove any records from A.
In your case, you can simply move the ON clause from the LEFT JOIN to the end of the following INNER JOIN.
SELECT
PMEOBJECT.OBJECTID
,PMEOBJECTVALIDITY.VALIDFROM
,PMEOBJECTDIMENSION.DIMENSION2_
FROM PMEOBJECT
LEFT JOIN PMEOBJECTVALIDITY
INNER JOIN(
SELECT
OBJECTID,
MAX(VALIDFROM) AS NEWFROMDATE,
MAX(VALIDTO) AS NEWTODATE
FROM PMEOBJECTVALIDITY B
GROUP BY OBJECTID
) B
ON PMEOBJECTVALIDITY.OBJECTID = B.OBJECTID
AND PMEOBJECTVALIDITY.VALIDFROM = B.NEWFROMDATE
ON PMEOBJECTVALIDITY.OBJECTID = PMEOBJECT.OBJECTID
AND PMEOBJECTVALIDITY.DATAAREAID = PMEOBJECT.DATAAREAID --here it is!
LEFT JOIN PMEOBJECTDIMENSION
INNER JOIN(
SELECT
OBJECTVALIDITYID,
MAX(VALIDFROM) AS NEWFROMDATE_2
FROM PMEOBJECTDIMENSION C
GROUP BY OBJECTVALIDITYID
) C
ON PMEOBJECTDIMENSION.OBJECTVALIDITYID = C.OBJECTVALIDITYID
AND PMEOBJECTDIMENSION.VALIDFROM = C.NEWFROMDATE_2
ON PMEOBJECTDIMENSION.OBJECTVALIDITYID = PMEOBJECTVALIDITY.RECID
AND PMEOBJECTDIMENSION.DATAAREAID = PMEOBJECTVALIDITY.DATAAREAID --I'm here