試してはいけませんが、自分の目で確かめてください:-)
そして、テーブルへのアクセスは1つだけです。
あなたのテーブル：
SQL> create table mytable (tid,tname,effectivedate)
2 as
3 select 1, 'A', date '2011-07-01' from dual union all
4 select 2, 'A', date '2011-08-01' from dual union all
5 select 3, 'A', date '2011-09-01' from dual union all
6 select 4, 'A', date '2011-10-01' from dual union all
7 select 5, 'B', date '2011-08-01' from dual union all
8 select 6, 'B', date '2011-09-01' from dual union all
9 select 7, 'B', date '2011-10-01' from dual union all
10 select 8, 'C', date '2011-09-01' from dual
11 /
Table created.
そして、2つのテストケース：
SQL> var TODAY varchar2(10)
SQL> exec :TODAY := '2011-09-10'
PL/SQL procedure successfully completed.
SQL> select tid
2 , tname
3 , effectivedate
4 , case
5 when to_date(:TODAY,'yyyy-mm-dd') >= effectivedate
6 and to_date(:TODAY,'yyyy-mm-dd') < next_effectivedate
7 then
8 'Valid'
9 when to_date(:TODAY,'yyyy-mm-dd') >= effectivedate
10 then
11 'Invalid'
12 else
13 'Inactive'
14 end status
15 from ( select tid
16 , tname
17 , effectivedate
18 , lead(effectivedate,1,date '9999-12-31') over (partition by tname order by effectivedate) next_effectivedate
19 from mytable
20 )
21 /
TID T EFFECTIVEDATE STATUS
---------- - ------------------- --------
1 A 01-07-2011 00:00:00 Invalid
2 A 01-08-2011 00:00:00 Invalid
3 A 01-09-2011 00:00:00 Valid
4 A 01-10-2011 00:00:00 Inactive
5 B 01-08-2011 00:00:00 Invalid
6 B 01-09-2011 00:00:00 Valid
7 B 01-10-2011 00:00:00 Inactive
8 C 01-09-2011 00:00:00 Valid
8 rows selected.
SQL> exec :TODAY := '2011-10-02'
PL/SQL procedure successfully completed.
SQL> select tid
2 , tname
3 , effectivedate
4 , case
5 when to_date(:TODAY,'yyyy-mm-dd') >= effectivedate
6 and to_date(:TODAY,'yyyy-mm-dd') < next_effectivedate
7 then
8 'Valid'
9 when to_date(:TODAY,'yyyy-mm-dd') >= effectivedate
10 then
11 'Invalid'
12 else
13 'Inactive'
14 end status
15 from ( select tid
16 , tname
17 , effectivedate
18 , lead(effectivedate,1,date '9999-12-31') over (partition by tname order by effectivedate) next_effectivedate
19 from mytable
20 )
21 /
TID T EFFECTIVEDATE STATUS
---------- - ------------------- --------
1 A 01-07-2011 00:00:00 Invalid
2 A 01-08-2011 00:00:00 Invalid
3 A 01-09-2011 00:00:00 Invalid
4 A 01-10-2011 00:00:00 Valid
5 B 01-08-2011 00:00:00 Invalid
6 B 01-09-2011 00:00:00 Invalid
7 B 01-10-2011 00:00:00 Valid
8 C 01-09-2011 00:00:00 Valid
8 rows selected.
よろしくお願いいたします。
ロブ。