What is a best way to write SQL ?

Question

Sample Case
drop table t;
drop table b;
create table t ( a varchar2(4), b number, c varchar2(1));
insert into t values ('A00', 10, 'R');
insert into t values ('A01', 11, 'R');
insert into t values ('A02', 12, 'R');
insert into t values ('A03', 13, 'R');
insert into t values ('A00', 10, 'P');
insert into t values ('A01', 11, 'P');
insert into t values ('A02', 12, 'P');
insert into t values ('A03', 13, 'P');
commit;
create table b ( j varchar(4), k varchar2(1), l varchar2(5), m number(3), n varchar2(5), o number(3));
insert into b values ('A00', 'P', 'FIXED', 100, 'FLOAT', 60);
insert into b values ('A01', 'P', 'FIXED', 101, 'FIXED', 30);
insert into b values ('A02', 'R', 'FLOAT', 45, 'FLOAT', 72);
insert into b values ('A03', 'R', 'FIXED', 55, 'FLOAT', 53);
commit;
10:19:13 SQL> select * from t;
A B C
A00 10 R
A01 11 R
A02 12 R
A03 13 R
A00 10 P
A01 11 P
A02 12 P
A03 13 P
8 rows selected.
10:19:19 SQL> select * from b;
J K L M N O
A00 P FIXED 100 FLOAT 60
A01 P FIXED 101 FIXED 30
A02 R FLOAT 45 FLOAT 72
A03 R FIXED 55 FLOAT 53
1/     In table t each reference having 2 records one with P another is with R
2/     In table b each refrence merged into single record and there are many records which are not existing in table t
3/      both t and j tables can be joined using a = j
4/     If from table t for a reference indicator is 'P' then if have to pick up l and m columns, if it is 'R' then I have to pick up n and o columns
5/     I want output in following format
A00     P     FIXED          100
A00     R     FLOAT          60
A01     P     FIXED          101
A01     R     FIXED          30
A02     P     FLOAT          72
A02     R     FLOAT          45
A03     P     FLOAT          53
A03     R     FIXED          55
6/     Above example is a sample ouput, In above example I have picked up only l,m,n,o columns, but in real example there are many columns ( around 40 ) to be selected. ( using "case when" may not be practical )
Kindly suggest me what is a best way to write SQL ?
thanks & regards
pjp

Answer 1

Is this?
select b.j,t.c as k,decode(t.c,'P',l,n) as l,decode(t.c,'P',m,o) as m
from t,b
where t.a=b.j
order by j,k
J K L M
A00 P FIXED 100
A00 R FLOAT 60
A01 P FIXED 101
A01 R FIXED 30
A02 P FLOAT 45
A02 R FLOAT 72
A03 P FIXED 55
A03 R FLOAT 53
8 rows selected.
or is this?
select b.j,t.c as k,decode(t.c,b.k,l,n) as l,decode(t.c,b.k,m,o) as m
from t,b
where t.a=b.j
order by j,k
J K L M
A00 P FIXED 100
A00 R FLOAT 60
A01 P FIXED 101
A01 R FIXED 30
A02 P FLOAT 72
A02 R FLOAT 45
A03 P FLOAT 53
A03 R FIXED 55
8 rows selected.