ms access query very slow - sql

Question

I have this ms access query:
SELECT t1.sb, suchbegriff2, menge
FROM (SELECT artnr & '/' & [lfdnr-kal] AS sb, left(suchbegriff,7) &
val(right(suchbegriff,4)) AS suchbegriff2
FROM kvks
WHERE suchbegriff like '*/*') AS t1
INNER JOIN (SELECT artnr & '/' & [lfdnr-kal] AS sb,
[artnr-hz] & '/' & val(lfdnr) AS hz, menge
FROM konf
WHERE [artnr-hz]<>'') AS t2
ON (t1.sb=t2.sb) AND (t1.suchbegriff2=t2.hz);
It runs really very slow (over 30 sec.). I figured out, it is because the inner join part. If I leave this, the speed is correct.
Maybe it is because of the fact slow, that the joined fields are calculated expressions?
EDIT:
I modified the query based on the answer of Smandoli:
SELECT kvks.artnr & '/' & kvks.[lfdnr-kal] AS sb,
left(suchbegriff,7) & val(right(suchbegriff,4)) AS suchbegriff2,
konf.menge
FROM kvks, konf
WHERE kvks.suchbegriff like '*/*'
and konf.[artnr-hz]<>''
and kvks.artnr=konf.artnr
and kvks.[lfdnr-kal]=konf.[lfdnr-kal]
and left(suchbegriff,7) & val(right(suchbegriff,4))=[artnr-hz] & '/' & val(lfdnr)
It runs now correct.
Thanks for your contribution.

Answer 1

You do have a complicated mess with those calculated fields. Why not join more directly? This query below leaves one '/' unaccounted for, but should tell you what I'm thinking of.
SELECT
t1.sb,
left(st1.uchbegriff,7) & val(right(t1.suchbegriff,4)) AS suchbegriff2,
t1.menge
FROM kvks AS t1
INNER JOIN konf AS t2
WHERE (t1.suchbegriff like '*/*')
AND (t2.artnr-hz<>'')
AND (t1.artnr=t2.artnr)
AND (t1.lfdnr-kal=t2.lfdnr-kal)
AND (left(t1.suchbegriff,7)=t1.[artnr-hz])
AND (val(right(t1.suchbegriff,4))=val(t2.hz));

Answer 2

For the inner join, you can try to use a saved query (or temp table) instead of writing the query at run time.
So, I would first try to abstract this query
SELECT artnr & '/' & [lfdnr-kal] AS sb,
[artnr-hz] & '/' & val(lfdnr) AS hz, menge
FROM konf
WHERE [artnr-
hz]<>'') AS t2
ON (t1.sb=t2.sb) AND (t1.suchbegriff2=t2.hz)
Second of all, if possible, I would abstract some of the functions in the queries. You could do this with VBA, or manipulating the data outside of the queries.
Third, you could always create a field on your table that combines the two fields together that you need.
E.x: Make a new column in your konf table that stores the value of artnr & '/' & [lfdnr-kal]
What you need to do is limit the functions/calculations/coalescing of fields at run time. That's a lot for a query to do, and if it's running slow I would see a direction correlation either between that, or something incorrect with your indexes/joins.
If you've identified this as a join issue, you can use VBA to spin up a temp table with your queries, and use those as the record source instead of the SQL.
Also, if you don't utilize a temp table, at least save the queries. This allows Access to have a plan for running the queries, whereas your query is 100% run-time dependent.

Answer 3

Your query runs slow because of "Nesting" and then "Joining". You can try creating the temp tables and used that table in query. Creating temp table is good practice rather than making the query complex.

Answer 4

99999!!! I think you have just to implement some index
(t1.sb=t2.sb) AND (t1.suchbegriff2=t2.hz);
these ones are very suspicious. Are the 4 indexed?