SQL query to retrieve last record from a linked table [duplicate] - sql

Question

This question already has answers here:
SQL join: selecting the last records in a one-to-many relationship
(13 answers)
Closed 6 years ago.
I wrote a query to compare 2 columns in different tables (TRELAY VS TUSERDEF8). The query works great, except that it retrieves the top record in the TUSERDEF8 table which has a many to one relationship to the TRELAY table.
The tables are linked by TRELAY.ID = TUSERDEF8.N01. I would like to retrieve the latest record from TUSERDEF8 and compare that record with the TRELAY record. I plan to use the max value of the index column (TUSERDEF8.ID) to determine the latest record.
I am using SQL Server.
My code is below, but I'm not sure how to change the query to retrieve the last TUSERDEF8 record. Any help is appreciated.
SELECT
TRELAY.ID, TRELAY.S15,
TUSERDEF8.S04, TUSERDEF8.N01, TUSERDEF8.S06
FROM
TRELAY
INNER JOIN
TUSERDEF8 ON TRELAY.ID = TUSERDEF8.N01
WHERE
LEFT(TRELAY.S15, 1) <> LEFT(TUSERDEF8.S04, 1)
AND NOT (TRELAY.S15 LIKE '%MEDIUM%' AND
TUSERDEF8.S04 LIKE '%N/A%' AND
TUSERDEF8.S06 LIKE '%EACMS%')

Answer 1

Making the assumption that your IDs are int(s) then the below might work?
SELECT TOP 1 TRELAY.ID, TRELAY.S15, TUSERDEF8.S04, TUSERDEF8.N01, TUSERDEF8.S06
FROM TRELAY INNER JOIN TUSERDEF8
ON TRELAY.ID = TUSERDEF8.N01
WHERE LEFT(TRELAY.S15, 1) <> LEFT(TUSERDEF8.S04, 1)
AND NOT (
TRELAY.S15 LIKE '%MEDIUM%'
AND TUSERDEF8.S04 LIKE '%N/A%'
AND TUSERDEF8.S06 LIKE '%EACMS%'
)
ORDER BY TUSERDEF8.ID DESC
HTH
Dave

Answer 2

You could do this:
With cteLastRecord As
(
Select S04, N01, S06,
Row_Number() Over (Partition By N01, Order By ID Desc) SortOrder
From TUSERDEF8
)
SELECT
TRELAY.ID, TRELAY.S15,
TUSERDEF8.S04, TUSERDEF8.N01, TUSERDEF8.S06
FROM
TRELAY
INNER JOIN
(Select S04, N01, S06 From cteLastRecord Where SortOrder = 1) TUSERDEF8 ON TRELAY.ID = TUSERDEF8.N01
WHERE
LEFT(TRELAY.S15, 1) <> LEFT(TUSERDEF8.S04, 1)
AND NOT (TRELAY.S15 LIKE '%MEDIUM%' AND
TUSERDEF8.S04 LIKE '%N/A%' AND
TUSERDEF8.S06 LIKE '%EACMS%')

Answer 3

I believe that your expected output is still a little ambiguous.
It sounds to me like you want only the record from the output where TUSERDEF8.ID is at its max. If that's correct, then try this:
SELECT TRELAY.ID, TRELAY.S15, TUSERDEF8.S04, TUSERDEF8.N01, TUSERDEF8.S06
FROM TRELAY
INNER JOIN TUSERDEF8 ON TRELAY.ID = TUSERDEF8.N01
WHERE LEFT(TRELAY.S15, 1) <> LEFT(TUSERDEF8.S04, 1)
AND NOT (TRELAY.S15 LIKE '%MEDIUM%' AND
TUSERDEF8.S04 LIKE '%N/A%' AND
TUSERDEF8.S06 LIKE '%EACMS%')
AND TUSERDEF8.ID IN (SELECT MAX(TUSERDEF8.ID) FROM TUSERDEF8)
EDIT: After reviewing your recent comments, it would seem something like this would be more suitable:
SELECT
, C.ID
, C.S15,
, D.S04
, D.N01
, D.S06
FROM (
SELECT A.ID, A.S15, MAX(B.ID) AS MaxID
FROM TRELAY AS A
INNER JOIN TUSERDEF8 AS B ON A.ID = B.N01
WHERE
LEFT(A.S15, 1) <> LEFT(B.S04, 1)
AND NOT (A.S15 LIKE '%MEDIUM%' AND
B.S04 LIKE '%N/A%' AND
B.S06 LIKE '%EACMS%')
GROUP BY A.ID, A.S15
) AS C
INNER JOIN TUSERDEF8 AS D ON C.ID = D.N01 AND C.MaxID = D.ID

Answer 4

Using an ID column to determine which row is "last" is a bad idea
Using cryptic table names like "TUSERDEF8" (how is it different from TUSERDEF7) is a very bad idea, along with completely cryptic column names like "S04".
Using prefixes like "T" for table is a bad idea - it should already be clear that it's a table.
Now that all of that is out of the way:
SELECT
R.ID,
R.S15,
U.S04,
U.N01,
U.S06
FROM
TRELAY R
INNER JOIN TUSERDEF8 U ON U.N01 = R.ID
LEFT OUTER JOIN TUSERDEF8 U2 ON
U2.N01 = R.ID AND
U2.ID > U.ID
WHERE
U2.ID IS NULL AND -- This will only happen if the LEFT OUTER JOIN above found no match, meaning that the row in U has the highest ID value of all matches
LEFT(R.S15, 1) <> LEFT(U.S04, 1) AND
NOT (
R.S15 LIKE '%MEDIUM%' AND
U.S04 LIKE '%N/A%' AND
U.S06 LIKE '%EACMS%'
)