almost ;-)
I used the suggestion with a virtual field in a test system.
taana made this Select (as found per st04, cursor cache)
>>
SELECT "CLIENT"
FROM "ADRC"
WHERE "CLIENT"=:A0
<<
(where "CLIENT" is the MANDT field in DB-table ADRC)
=>
Thus taana only counts lines of the current Client/Mandt.
So I tried db05:
db05 made this Select:
>>
SELECT "CLIENT"
FROM "ADRC"
ORDER BY "CLIENT"
<<
at least it gives a vague idea about the number of different clients,
and the selectivity/distribution of Client/Mandt.
HTH