Use of cursors insted of select statements

Question

could any one please explain what is the advantage of using cursors instead of simple select statements
thanks
siby

Answer 1

A benefit to using an explicit cursor rather than a select statement, is for the NO_DATA_FOUND exception. Its kind of like a free IF statment. IF no data is found, then stop.
if you write a select statement, and no data is returned, you SHOULD code for the NO_DATA_FOUND exception. Often people say, "i'll ALWAYS get a row returned". but you should always cover your code "just in case". so you must code an exception...
declare
v_var varchar2(1);
procedure do_something(p_parm varchar2) is
begin
null;
end do_something;
procedure log_error is
begin
null;
end log_error;
begin <<main>>
do_something('x');
begin <<selectblock>>
select dummy
into v_var
from dual
where dummy = 'a';
do_something(v_var);
exception
when no_data_found then
log_error;
end selectblock;
do_something (v_var||'abc');
end main;
if you use an explicit cursor instead, you don't need to code for the NO_DATA_FOUND. If an explicit cursor opens and finds no rows, there are simply no rows. of course, you don't need a loop if you expect only 1 row returned under normal circumstances.
BTW, don' forget that SQL%ROWCOUNT and your_cursor%ROWCOUNT are not initialized. There is a null, until a row is successfully fetched. therefore if no rows are returned at all, %ROWCOUNT is NULL.
declare
v_var varchar2(1);
cursor my_cur is
select dummy
from dual
where dummy = 'a';
procedure do_something(p_parm varchar2) is
begin
null;
end do_something;
procedure log_error is
begin
null;
end log_error;
begin << main>>
for cur_rec in my_cur loop
dbms_output.put_line('inside');
begin <<loop_block>>
if nvl(my_cur%rowcount,0) > 1 then
do_something(cur_rec.dummy);
else
log_error;
end if;
end loop_block;
end loop;
end main;
/