Double Lookups?

Question

I am struggling with something that I suspect is kindof basic. I would like to produce a report that is based on the need for multiple value lookups per line on a report. The data table contains:
Index, partid, parentid…….
The lookup contains:
Part_index, part_name
I would like my report to show
Index, partid, part_name, parentid, parent_name.
So I can show the part name instead of the id, for both parent and child. I cannot work out how to implement the “double lookup” of the names.
My best guess is something like below.
select
"MYINDEX",
"PART_ID",
(select PART_NAME from NAME_LOOKUP where "NAME_LOOKUP"."PART_INDEX"="PARTS"."PART_ID") as "Part Name",
"PARENT_ID",
(select PART_NAME from NAME_LOOKUP where "NAME_LOOKUP"."PART_INDEX"="PARTS"."PARENT_ID") as "Parent Name"
from "#OWNER#"."PARTS"
Thanks in advance for any suggestions.
J

Answer 1

Hi,
You can also do this with a self-join, which may be faster.
select     "MYINDEX",
     "PART_ID",
     part_lookup.PART_NAME     AS "Part Name",
     "PARENT_ID",
     parent_lookup.PART_NAME     AS "Parent Name"
from     "#OWNER#"."PARTS"
JOIN     NAME_LOOKUP     part_lookup
ON     part_lookup."PART_INDEX"     = "PARTS"."PART_ID"
JOIN     NAME_LOOKUP     parent_lookup
ON     parent_lookup."PART_INDEX"     = "PARTS"."PARENT_ID"
;This still has your original typo.
If there are parts that do not have matches in the name_lookup table, then change the JOINs to LEFT OUTER JOINs.