Creating a complex view

Question

I Need to create a complex (at least for me !!)view can some body throw some ideas
I have two tables
TABLE-1
NAME     SYSTEM          DT
AAA     GRADE-A          DATE
AAA     GRADE-B          DATE
BBB     GRADE-A          DATE
BBB     GRADE-B          DATE
CCC     GRADE-B          DATE
TABLE-2
NAME     SYSTEM          DT
DDD     GRADE-C          DATE
AAA     GRADE-C          DATE
BBB     GRADE-C          DATE
CCC     GRADE-C          DATE
Now I need to create a view with following details.
PV_MYVIEW
CLASS          DT
CLASS-A          DATE-A
CLASS-B          DATE-B
Where as date DATE-A should be oldest date (least) from following
Table-1.date where name=AAA And SYSTEM=GRADE-A
Table-1.date where name=AAA And     SYSTEM=     GRADE-B
Table-1.date where name=BBB And     SYSTEM=     GRADE-A
Table-1.date where name=BBB And     SYSTEM=     GRADE-B
Table-1.date where name=CCC And     SYSTEM=     GRADE-B
Table-2.date where name=DDD And     SYSTEM=     GRADE-C
Table-2.date where name=AAA And     SYSTEM=     GRADE-C
Table-2.date where name=BBB And     SYSTEM=     GRADE-C
Table-2.date where name=CCC And     SYSTEM=     GRADE-C
Where as DATE-B should be oldest date (least) from following
Table-1.date where name=AAA And     SYSTEM=     GRADE-A
Table-1.date where name=AAA And     SYSTEM=     GRADE-B
Table-1.date where name=BBB And     SYSTEM=     GRADE-A
Table-1.date where name=BBB And     SYSTEM=     GRADE-B
Table-2.date where name=AAA And     SYSTEM=     GRADE-C
Table-2.date where name=BBB And     SYSTEM=     GRADE-C
As a solution for this, I Am thinking of first creating a intermediate view which comsist
Class, Name and Date and then from this view creating PV_MYVIEW..
Am i in right direction?
THanks in advnce for your time

Answer 1

creating an intermediate view is the worst thing to do!
try this
select
'CLASS-A' class, min(dt) DT
from
select DT from TABLE1
where (name='AAA' And SYSTEM='GRADE-A')
or (name='AAA' And SYSTEM='GRADE-B')
or (name='BBB' And SYSTEM='GRADE-A')
or (name='BBB' And SYSTEM='GRADE-B')
or (name='CCC' And SYSTEM='GRADE-B')
union all
select DT from TABLE2
where (name='AAA' And SYSTEM='GRADE-C')
or (name='BBB' And SYSTEM='GRADE-C')
or (name='CCC' And SYSTEM='GRADE-C')
or (name='DDD' And SYSTEM='GRADE-C')
union all
select
'CLASS-B', min(dt)
from
select DT from TABLE1
where (name='AAA' And SYSTEM='GRADE-A')
or (name='AAA' And SYSTEM='GRADE-B')
or (name='BBB' And SYSTEM='GRADE-A')
or (name='BBB' And SYSTEM='GRADE-B')
union all
select DT from TABLE2
where (name='AAA' And SYSTEM='GRADE-C')
or (name='BBB' And SYSTEM='GRADE-C')
You can for sure remove some duplicate clause and you should verify that the specifications are accurate
REgards
Laurent