How to execute one procedure within another procedure - oracle

Question

Hi I am writing one procedure which will be called by the program and this procedure will further call to another procedure to perform different business logic. so I did something like this.
PROCEDURE calculator(service_id IN NUMBER, amount IN NUMBER) as
p_proc_name varchar(100);
begin
select sc.procedure_name into p_proc_name from test.procedure sc where sc.service_config_id = service_id;
begin
execute immediate (p_proc_name) using 1;
exception when NO_DATA_FOUND then
DBMS_OUTPUT.PUT_LINE('p_proc_name = ' || p_proc_name);
end;
end sb_referal_calculator;
PROCEDURE f_service(amount IN NUMBER) as
cmpany_id NUMBER;
service_date date;
leases_days NUMBER;
referal_amount Number;
requested_quote_id number :=1;
begin
referal_amount :=0;
DBMS_OUTPUT.PUT_LINE('service_date = ');
end f_service;
PROCEDURE d_service(amount IN NUMBER) as
cmpany_id NUMBER;
service_date date;
leases_days NUMBER;
referal_amount Number;
requested_quote_id number :=1;
begin
referal_amount :=0;
DBMS_OUTPUT.PUT_LINE('service_date = ');
end d_service;
So here calcultor procedure will find the another procedure name dynamically and try to execute it with parameter. But it gives an error.
It is just a test program.
Executing PL/SQL: CALL DBMS_DEBUG_JDWP.CONNECT_TCP( '10.1.26.70', '55891' )
Debugger accepted connection from database on port 55891.
ORA-00900: invalid SQL statement
ORA-06512: at "test.demo_pkg", line 38
ORA-06512: at line 8
Executing PL/SQL: CALL DBMS_DEBUG_JDWP.DISCONNECT()
Process exited.
I really do not how this procedure will work to perform this task. I remembered it was running and I was doing testing. But really do not what i have did and stop working.
Please correct me what i doing wrong.
Thanks

Answer 1

When you use execute immediate it runs the dynamic statement in an SQL context that isn't able to see your PL/SQL context. That has several impacts here. Firstly, you have to call your procedure from PL/SQL so you need to create an anonymous block, as Egor Skriptunoff said, and exactly the format you need depends on what the table (and thus your vaiable) contains. The shortest it might be is:
execute immdiate 'begin ' || p_proc_name || ' end;' using 1;
But that assumes the varible contains a value like:
test_pkg.d_service(:arg);
If it only contains the name of the procedure with no arguments and no package qualifier, i.e. just d_service, it might need to be as much as:
execute immdiate 'begin test_pkg.' || p_proc_name || '(:arg); end;' using 1;
Or something in between.
The other impact is that the procedure name has to be public as it is effectively being called from outside the package when it's invoked dynamically; so it has to be declared in the package specification. That may already be the case here from the order the procedures are appearing in the body.
But if you are always calling procedures in the same package, and since you must then have a limited number of possible values, it might be simpler to avoid dynamic SQL and use the value to decide which procedure to call:
case p_proc_name
when 'f_service' then
f_service(1);
when 'd_service' then
d_service(1);
-- etc.
end case;
That also lets you call private procedures.