DB2 SQL SELECT前1个具有连接的组

Question

I'm connecting to a DB2 database and want to use the Max(PO180M1.POORDT) or the TOP 1 grouping by the PO180M2.PHPPN (PARTNO). How would I do this? I think I keep getting close but not getting it to work.

SELECT PO180M2.PHPPN AS PartNo, (PO180M2.PHVNPD || ' ' || PO180M2.PHVNP2) AS PartDesc, 
       PO180M1.POORDT AS OrderDate, PO180M2.PHUNCT AS UnitCost
FROM PO180M1, PO180M2 
WHERE PO180M1.POORNO = PO180M2.PHORNO 
ORDER BY PartNo, OrderDate DESC

Answer 1

Almost got it. With any aggregates, Max() , Min() , Avg() , Count() , Sum() , a GROUP BY clause is required listing the "level" columns which usually are indicator fields (names, categories, types).

Also, you will leave out a level column that you are trying to run an aggregate, here being POORDT . Finally, you will not be able to ORDER BY the very aggregated field but only the group fields listed.

SELECT PO180M2.PHPPN AS PartNo, (PO180M2.PHVNPD || ' ' || PO180M2.PHVNP2) AS PartDesc, 
       PO180M2.PHUNCT AS UnitCost, Max(PO180M1.POORDT) As MaxPOORDT
FROM PO180M1 
INNER JOIN PO180M2 ON PO180M1.POORNO = PO180M2.PHORNO 
GROUP BY PO180M2.PHPPN, (PO180M2.PHVNPD || ' ' || PO180M2.PHVNP2), PO180M2.PHUNCT
ORDER BY PartNo

By the way, I noticed you used the older syntax of table joins listing tables in FROM clause with a WHERE clause. I changed it to an INNER JOIN with ON which I believe is compliant with DB2.