SQL Function and Anonymous block - sql

Question

I'm taking a class about databases. I am very new to it, so excuse me if this is an obvious error, but I've been working on this problem for hours and not sure what else to do.
The code is suppose to create a function to that
A.) Outputs the average netwin for a year given by a parameter
(given by the formula (SeasonW-Seasonl) + (PlayoffW - PlayoffL)
B.) Outputs all of the coaches that have a netwin over the average
C.) Returns the number of coaches that fits this criteria.
D.)Have a anonymous block that calls this function, and outputs two different messages depending on the return on the function.
Now I have sucessfully done parts A, C, and D. But for some reason my function will not be created when I insert part B.
create or replace function GOOD_COACHES(season IN INT)
return INT
IS
netwin INT;
CNT INT;
BEGIN
--Calculated netwin
select AVG((SEASON_WIN-SEASON_LOSS) + (PLAYOFF_WIN-PLAYOFF_LOSS)) into netwin from COACHESSEASON where YEAR = season;
--Prints out A
dbms_output.put_line('Average Netwin is: ' || netwin);
--This Line messes up the function, I don't know why
select T.FIRSTNAME, T.LASTNAME from COACHESSEASON T where ((T.SEASON_WIN-T.SEASON_LOSS) + (T.PLAYOFF_WIN-T.PLAYOFF_LOSS))>netwin and YEAR = season;
--Calculates the number of teams that satisfy average
select count(T.FIRSTNAME) into CNT from COACHESSEASON T where ((T.SEASON_WIN-T.SEASON_LOSS) + (T.PLAYOFF_WIN-T.PLAYOFF_LOSS))>netwin and YEAR = season;
return CNT;
END;
--End of the Function
--Start of the Anonymous Block
DECLARE
x int := GOOD_COACHES(1998);
BEGIN
if x = 0 then dbms_output.put_line('We didn''t find any good_coaches!');
else dbms_output.put_line('The No. of good coaches is ' || x);
end if;
END;
/
That third line in the function messes it up and doesn't allow it to be called. If I comment it out, it works properly.
When I take it out of the function and make it into a regular SQL statement, it works.
select T.FIRSTNAME, T.LASTNAME from COACHESSEASON T where ((T.SEASON_WIN-T.SEASON_LOSS) + (T.PLAYOFF_WIN-T.PLAYOFF_LOSS))>0 and YEAR = /*RandYear*/;
If anyone understands why the function can not be created with that line it in, I would appreciate the advice. I also do not know how I would print out the results of the selected row in the function.

Answer 1

You are not selecting the T.FIRSTNAMEs and T.LASTNAMEs into anything so the statement is not valid for inclusion in a PL/SQL block.
There are likely to be multiple "good coaches" so you can't put the values into a single variable and will have to use a cursor or a collection.
Using collections, if you create a table type to collect the first and last names into:
CREATE TYPE VARCHAR2s_Table AS TABLE OF VARCHAR2(30);
/
Then you can use this to collect the first and last names (and as a bonus the collection size will tell you how many good coaches there are and you can skip the last query):
create or replace function GOOD_COACHES(season IN INT)
return INT
IS
netwin INT;
CNT INT;
firstnames VARCHAR2s_Table;
lastnames VARCHAR2s_Table;
BEGIN
--Calculated netwin
select AVG((SEASON_WIN-SEASON_LOSS) + (PLAYOFF_WIN-PLAYOFF_LOSS))
into netwin
from COACHESSEASON
where YEAR = season;
--Prints out A
dbms_output.put_line('Average Netwin is: ' || netwin);
--This Line messes up the function, I don't know why
select T.FIRSTNAME, T.LASTNAME
BULK COLLECT INTO firstnames, lastnames
from COACHESSEASON T
where ((T.SEASON_WIN-T.SEASON_LOSS) + (T.PLAYOFF_WIN-T.PLAYOFF_LOSS))>netwin
and YEAR = season;
FOR i IN 1 .. firstnames.COUNT LOOP
DBMS_OUTPUT.put_line( firstnames(i) || ' ' || lastnames(i) );
END LOOP;
return firstnames.COUNT;
END;
/
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