Question

I have 3 tables.

driver, trip, tripLegs

In driver table the columns are E#, L#, STATUS.
In trip table the columns are T#, L#, REG#, trip_DATE
In tripLeg table the columns are T#, LEG#, DEPARTURE, DESTINATION

First I tried a sql query which is:

select d.l#, count(tg.leg#) as total_no_of_legs
from driver d left outer join trip t on (d.l# = t.l#)
left outer join tripleg tg on (t.t# = tg.t#)
group by d.l#;

Results i got was:

L#         Total_no_of_legs
-----------------------------
11111        20

and so on.

This is the total number of legs from all T#’s leg#
e.g

T#1 's leg# = 3
T#2's leg# = 10
T#3's leg# = 7

Total = 20 that is why L# 11111 total no of Legs is 20.
But I wanna find out the max leg# of each L# which is 10.
How do I do a query to find out highest number of LEG# group by T#?

Afterwhich, how do I really start to convert this into a PL/SQL statement?

Have been wondering all day and reading up on books. Still couldnt find a solution to it

Answer 1

But I wanna find out the max leg# of each L#

Maybe I’m missing something, but isn’t that simply:

select d.l#, 
       max(tg.leg#) as max_leg_nr
from driver d 
  left outer join trip t on (d.l# = t.l#)
  left outer join tripleg tg on (t.t# = tg.t#)
group by d.l#

I don’t see the need to put this into a stored procedure.

To put this into a function that returns the result, you need a pipelined function:

create type leg_info as object (l# integer, max_leg_nr integer);
/

create type leg_info_list as table of leg_info
/

create or replace function get_max_leg_info
  return leg_info_list
  PIPELINED
as
  r_info leg_info;
begin
   r_info := leg_info(null, null);
   for p_rec in ( .... here goes the select ... )
   loop
     r_info.l# := p_rec.l#;
     r_info.max_leg_nr := p_rec.max_leg_nr ;
     pipe row(r_row);
   end loop;
   return;
end;
/

You can then use this function like this:

select *
from table(get_max_leg_info())