Select Query not workin as expected

Question

HI Guru's,
Here is a select query which takes more time when I incerase the search criteria . The Table I_MKPF is not initial.
select mblnr mjahr zeile bwart matnr werks charg lifnr
shkzg bwtar menge meins ebeln aufnr bukrs prctr
from mseg into corresponding fields of table z_rec
for all entries in i_mkpf
where
mblnr eq i_mkpf-mblnr and
mjahr eq i_mkpf-mjahr and
bwart in s_bwart and
werks in s_werks and
bukrs in s_bukrs.
In the above query MBLNR and MJAHR are primary key fields in the same order as in the database.
The query fetches 2 records and takes around 20 minutes.
I did some more testing and found one peculiar issue.
The query takes long time only when S_WERKS and/or S_BUKRS is entered on the selection screen.
If these two fields are left blank it works super quick.
I am baffled as to why this is happening. Should it not have been the other way around..?
Could please take a look and tell me what the issue might be??
Thanks in Advance,
Imran

Answer 1

Hi Imran,
please check the SQL performance in transaction ST05 > "Explaine one SQL request" for this slightly modified statement:
select mblnr, mjahr, zeile, bwart, matnr, werks, charg, lifnr,
shkzg, bwtar, menge, meins, ebeln, aufnr bukrs, prctr
from mseg
where
mblnr = '1' and
mjahr = '2' and
bwart in ('1', '2') and
werks in ('1', '2') and
bukrs in ('1', '2')
or
mblnr = '1' and
mjahr = '2' and
bwart in ('1', '2') and
werks in ('1', '2') and
bukrs in ('1', '2')
or
mblnr = '1' and
mjahr = '2' and
bwart in ('1', '2') and
werks in ('1', '2') and
bukrs in ('1', '2')
or
mblnr = '1' and
mjahr = '2' and
bwart in ('1', '2') and
werks in ('1', '2') and
bukrs in ('1', '2')
Please answer back with the results. Best regards,
Alvaro