Ambiguous column name 'DELETED' when filtering

Question

Good morning.

Without saying to much, I am joining two tables where each contain a row with the same name field DELETED. I am able to join both tables and get results, the problem is when I try to filter out those orders that are DELETED "X" and not DELETED "NULL", I get the ambiguous column name.

SELECT

OCRI.DDORD#,
OCRH.DCBCUS,
OCRI.DELETED

from ocri
join OCRH on DCORD# = DDORD#    
where OCRI.dditst <> 'C'
and DELETED <> 'X'

I have tried and OCRI.DELETED <> 'X' but then I get no results.

I would like to be able to filter out the X

DDORD#  DCBCUS     DELETED
194991  150482      NULL
195000  263609      X
195381  263609      X
195387  246045      NULL
195724  146551      NULL

Answer 1

Qualify ALL column references in your query. You haven't provided enough information to know which columns belong where.

Then, you need to handle NULL values.

An example:

SELECT rh.DDORD#, ri.DCBCUS, ri.DELETED
FROM ocri ri JOIN
     OCRH rh
     ON ri.DCORD# = rh.DDORD#    
WHERE rh.rhdditst <> 'C' AND
      (ri.DELETED <> 'X' OR ri.DELETED IS NULL);

Of course, I don't know what the tables look like so the qualifications are probably wrong.

Note that standard SQL has a NULL -safe comparison, which is supported by some databases. This looks like:

WHERE rh.rhdditst <> 'C' AND
      ri.DELETED IS DISTINCT FROM 'X';