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SELECT valueC
FROM C
INNER JOIN
(
SELECT DISTINCT lookupC
FROM B INNER JOIN
(
SELECT DISTINCT lookupB
FROM A
)
A2 ON B.id = A2.lookupB
)
B2 ON C.id = B2.lookupC
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select a.FirstName, a.LastName, v.District
from AddTbl a order by Firstname
natural join (select distinct LastName from
ValTbl v where a.LastName = v.LastName)