[SOLVED] Should I use an SQL full outer join for this?

Should I use an SQL full outer join for this?

Consider the following tables:

Table A:

DOC_NUM
DOC_TYPE
RELATED_DOC_NUM
NEXT_STATUS
...

Table B:

DOC_NUM
DOC_TYPE
RELATED_DOC_NUM
NEXT_STATUS
...

The DOC_TYPE and NEXT_STATUS columns have different meanings between the two tables, although a NEXT_STATUS = 999 means "closed" in both. Also, under certain conditions, there will be a record in each table, with a reference to a corresponding entry in the other table (i.e. the RELATED_DOC_NUM columns).

I am trying to create a query that will get data from both tables that meet the following conditions:

A.RELATED_DOC_NUM = B.DOC_NUM
A.DOC_TYPE = "ST"
B.DOC_TYPE = "OT"
A.NEXT_STATUS < 999 OR B.NEXT_STATUS < 999

A.DOC_TYPE = "ST" represents a transfer order to transfer inventory from one plant to another. B.DOC_TYPE = "OT" represents a corresponding receipt of the transferred inventory at the receiving plant.

We want to get records from either table where there is an ST/OT pair where either or both entries are not closed (i.e. NEXT_STATUS < 999).

I am assuming that I need to use a FULL OUTER join to accomplish this. If this is the wrong assumption, please let me know what I should be doing instead.

UPDATE (11/30/2021):

I believe that @Caius Jard is correct in that this does not need to be an outer join. There should always be an ST/OT pair.

With that I have written my query as follows:

SELECT <columns>
FROM A LEFT JOIN B
ON
    A.RELATED_DOC_NUM = B.DOC_NUM
WHERE
    A.DOC_TYPE IN ('ST') AND
    B.DOC_TYPE IN ('OT') AND
    (A.NEXT_STATUS < 999 OR B.NEXT_STATUS < 999)

Does this make sense?

UPDATE 2 (11/30/2021):

The reality is that these are DB2 database tables being used by the JD Edwards ERP application. The only way I know of to see the table definitions is by using the web site http://www.jdetables.com/, entering the table ID and hitting return to run the search. It comes back with a ton of information about the table and its columns.

Table A is really F4211 and table B is really F4311.

Right now, I've simplified the query to keep it simple and keep variables to a minimum. This is what I have currently:

SELECT CAST(F4211.SDDOCO AS VARCHAR(8)) AS SO_NUM,
       F4211.SDRORN AS RELATED_PO,
       F4211.SDDCTO AS SO_DOC_TYPE,
       F4211.SDNXTR AS SO_NEXT_STATUS,
       CAST(F4311.PDDOCO AS VARCHAR(8)) AS PO_NUM,
       F4311.PDRORN AS RELATED_SO,
       F4311.PDDCTO AS PO_DOC_TYPE,
       F4311.PDNXTR AS PO_NEXT_STATUS
FROM   PROD2DTA.F4211 AS F4211
       INNER JOIN PROD2DTA.F4311 AS F4311
         ON F4211.SDRORN = CAST(F4311.PDDOCO AS VARCHAR(8))
WHERE  F4211.SDDCTO IN ( 'ST' )
       AND F4311.PDDCTO IN ( 'OT' )

The other part of the story is that I'm using a reporting package that allows you to define "virtual" views of the data. Virtual views allow the report developer to specify the SQL to use. This is the application where I am using the SQL. When I set up the SQL, there is a validation step that must be performed. It will return a limited set of results if the SQL is validated.

When I enter the query above and validate it, it says that there are no results, which makes no sense. I'm guessing the data casting is causing the issue, but not sure.

UPDATE 3 (11/30/2021):

One more twist to the story. The related doc number is not only defined as a string value, but it contains leading zeros. This is true in both tables. The main doc number (in both tables) is defined as a numeric value and therefore has no leading zeros. I have no idea why those who developed JDE would have done this, but that is what is there.

So, there are matching records between the two tables that meet the criteria, but I think I'm getting no results because when I convert the numeric to a string, it does not match, because one value is, say "12345", while the other is "00012345".

Can I pad the numeric -> string value with zeros before doing the equals check?

UPDATE 4 (12/2/2021):

Was able to finally get the query to work by converting the numeric doc num to a left zero padded string.

SELECT <columns>
FROM   PROD2DTA.F4211 AS F4211
       INNER JOIN PROD2DTA.F4311 AS F4311
         ON F4211.SDRORN = RIGHT(CONCAT('00000000', CAST(F4311.PDDOCO AS VARCHAR(8))), 8)
WHERE  F4211.SDDCTO IN ( 'ST' )
       AND F4311.PDDCTO IN ( 'OT' )
       AND ( F4211.SDNXTR < 999
              OR F4311.PDNXTR < 999 )

Solution

You should write your query as follows:

SELECT <columns>
FROM A INNER JOIN B
ON
    A.RELATED_DOC_NUM = B.DOC_NUM
WHERE
    A.DOC_TYPE IN ('ST') AND
    B.DOC_TYPE IN ('OT') AND
    (A.NEXT_STATUS < 999 OR B.NEXT_STATUS < 999)

LEFT join is a type of OUTER join; LEFT JOIN is typically a contraction of LEFT OUTER JOIN). OUTER means "one side might have nulls in every column because there was no match". Most critically, the code as posted in the question (with a LEFT JOIN, but then has WHERE some_column_from_the_right_table = some_value) runs as an INNER join, because any NULLs inserted by the LEFT OUTER process, are then quashed by the WHERE clause