DECLARE
  l_my_cursor   sys_refcursor;
  l_stmt_str    VARCHAR2(32767);
  l_var         NUMBER;
BEGIN
  l_stmt_str :=
  'SELECT CASE WHEN 1=1 THEN 1 ELSE 2 END FROM dual
   UNION
   SELECT CASE WHEN 1=2 THEN 1 ELSE 2 END FROM dual';
  OPEN l_my_cursor FOR l_stmt_str;
    LOOP
      FETCH l_my_cursor
        INTO l_var;
       EXIT WHEN l_my_cursor%NOTFOUND;
      dbms_output.put_line('l_var='||to_char(l_var));
    END LOOP;
  CLOSE l_my_cursor;
END;

The above is applicable, when the sql returns only one value (1 row, 1 column)

How do I implement the same using curser,
ie, if the sql statement returns a tabular data (M rows, N columns:: where M & N >2)?

SELECT (CASE
           WHEN 1 = 1
              THEN CURSOR (SELECT 1
                             FROM DUAL)
           WHEN 1 = 2
              THEN CURSOR (SELECT 1
                             FROM DUAL)
           ELSE NULL
        END
       ) x
  FROM DUAL
/

It returned an error:
ORA-22902: CURSOR expression not allowed
Cause: CURSOR on a subquery is allowed only in the top-level SELECT list of a query.

That means you cannot use cursor expressions in a CASE or even DECODE.

Another solution may be the use of Dynamic SQL.

select *,
(case
when tb1.item=100 then
cursor(select * from tb2 where id=5 from mytable2 tb2)
when tb2.item=200 then
cursor(select * from tb3 where id=6 from mytable3 tb3)
else null
end ) curval
from mytable1

or would you have to used “decode”

I suggest you post your question on forums.oracle.com. I also suggest you read:

http://oraclesponge.blogspot.com/2005/04/writing-good-sql.html

And run the second OR if the:
(to_char(Adate, ‘YYYYMM’) = to_char(I_date, ‘YYYYMM’)
and “more_conditions”)
Didn´t returned rows.

But with the OR’s or with the UNION’s the query is to “heavy”.
Thats why the ideal would be run the query (based on three small queries) from the start to end, and “stop” at the first that returned rows.
I don’t know if thats possible. Besides the optional solution I refered before.

TIA,
SaSantos

select “fields”
from table
where
(to_char(Adate, ‘YYYYMMDD’) = to_char(I_date, ‘YYYYMMDD’)
and “more_conditions”)
OR
(to_char(Adate, ‘YYYYMM’) = to_char(I_date, ‘YYYYMM’)
and “more_conditions”)
OR
(to_char(Adate, ‘YYYY’) = to_char(I_date, ‘YYYY’)
and “more_conditions”)

Moreover, if Adate and I_date are of a date datatype, why converting to to_char? you can just use TRUNC.

select “fields”,
1 qry_condition
from table
where to_char(Adate, ‘YYYYMMDD’) = to_char(I_date, ‘YYYYMMDD’)
and “more_conditions”
union all
select “fields”,
2 qry_condition
from table
where to_char(Adate, ‘YYYYMM’) = to_char(I_date, ‘YYYYMM’)
and “more_conditions”
union all
select “fields”,
3 qry_condition
from table
where to_char(Adate, ‘YYYY’) = to_char(I_date, ‘YYYY’)
and “more_conditions”
order by “2″ — qry_condition;

The idea is to execute (only) the first query if results are returned, execute the next query if the first doesn’t returned rows, and execute the third query if none of the previous two return data.
But as we can conclude, everytime this cursor is executed it runs
all of the three queries that belong to it, which is impacting negatively the cursor perfomance.

One possible solution would be to divide it in three querys and use,
something like this:

open cursor1(L_date);
fetch cursor1 into …
if cursor1.notfound
then
open cursor2(L_date);
fetch cursor2 into …
if cursor2.notfound
then
open cursor3(L_date);
fetch cursor3 into …
if cursor3.notfound then
(…)

end if;

(…)

But personally I dont like this solution. I was thinking in use the CASE keyword to help me solving it, continuing to have only a single cursor. Something like this (I don’t know if this is possible):

select “fields”,
1 qry_condition
from table
where (
CASE when to_char(Adate, ‘YYYYMMDD’) = to_char(I_date, ‘YYYYMMDD’)
and “more_conditions”
then 1
—-
when to_char(Adate, ‘YYYYMM’) = to_char(I_date, ‘YYYYMM’)
and “more_conditions”
then 2
—-
when to_char(Adate, ‘YYYY’) = to_char(I_date, ‘YYYY’)
and “more_conditions”
then 3
end IN (1, 2, 3)
;

I know that this Oracle version of the PL/SQL doesn’t support the CASE, so I was thinking in using dynamic Sql to do it.
What’s your opinion, does the CASE solves my request or do you have a better solution?

Thanks in advance

SASantos