An execute query Procedure

Question

Hi guys, I'm starting to work in PL/SQL. I've got some experience in ms
sql server with T-SQL and I'm trying to understand some PL basis.
What
I want to do, is a stored procedure that returns the result of a given
query. Thats a simple thing to do in T-SQL. The code would be:
bq. create procedure runQuery(@someQuery varchar(200)) \\ *     as* \\ *     exec(@someQuery)* \\ *     return*
and the use of it would be:
bq. runQuery 'select 123' \\ *     -----------* \\ *     123*
bq. *(1 row(s) affected)*
Now, I'm trying to do the same thing in PL/SQL. What i've written by now is:
bq. CREATE OR REPLACE PROCEDURE RunQuery(someQuery IN VARCHAR2) \\ IS \\ BEGIN \\ EXECUTE IMMEDIATE someQuery ; \\ END; \\ */*
I got a messaje saying "procedure created", but when i try to use the procedure, it doesn't shows any results:
bq. begin \\ RunQuery('select from myTable');* \\ end; \\ */*
I just get a "Statement processed." message with out results.
Any idea of what I'm doing wrong?
thanks in advance
D

Answer 1

As Alex says, forget SQL Server, forget T-SQL as Oracle and PL/SQL are completely different.
If you need a procedure to open a dynamic query and pass the results back, the most usual way for this would be to use a REF CURSOR.
A ref cursor is simply a pointer to a query.
In the following example, the query is passed in to the function as a string. The function then executes (opens) the query and passes back a pointer to the query (the ref cursor)..
SQL> ed
Wrote file afiedt.buf
  1  create or replace function exec_query(p_query in varchar2) return sys_refcursor is
  2    v_rc sys_refcursor;
  3  begin
  4    OPEN v_rc FOR p_query;
  5    RETURN v_rc;
  6* end;
SQL> /
Function created.Now, within SQL*Plus (Oracle's command line SQL interface) we can declare a local variable of REFCURSOR type..
SQL> var x REFCURSOR;And then execute our function assigning the returned ref cursor back into our local variable..
SQL> exec :x := exec_query('select * from emp');
PL/SQL procedure successfully completed.Now, SQL*Plus has a local variable that points to the query, but no data has yet been fetched from it.
In SQL*Plus, to fetch the data we can use the "print" command..
SQL> print x
     EMPNO ENAME      JOB              MGR HIREDATE         SAL       COMM     DEPTNO
      7369 SMITH      CLERK           7902 17-DEC-80        800                    20
      7499 ALLEN      SALESMAN        7698 20-FEB-81       1600        300         30
      7521 WARD       SALESMAN        7698 22-FEB-81       1250        500         30
      7566 JONES      MANAGER         7839 02-APR-81       2975                    20
      7654 MARTIN     SALESMAN        7698 28-SEP-81       1250       1400         30
      7698 BLAKE      MANAGER         7839 01-MAY-81       2850                    30
      7782 CLARK      MANAGER         7839 09-JUN-81       2450                    10
      7788 SCOTT      ANALYST         7566 19-APR-87       3000                    20
      7839 KING       PRESIDENT            17-NOV-81       5000                    10
      7844 TURNER     SALESMAN        7698 08-SEP-81       1500          0         30
      7876 ADAMS      CLERK           7788 23-MAY-87       1100                    20
      7900 JAMES      CLERK           7698 03-DEC-81        950                    30
      7902 FORD       ANALYST         7566 03-DEC-81       3000                    20
      7934 MILLER     CLERK           7782 23-JAN-82       1300                    10
14 rows selected.
SQL>Et voila! our data is returned.
As another example, we can open up and fetch the data within a procedure itself..
SQL> ed
Wrote file afiedt.buf
  1  create or replace procedure proc_exec_query(p_query in varchar2) is
  2    v_rc sys_refcursor;
  3    TYPE t_rec IS RECORD (id NUMBER, name VARCHAR2(50));
  4    v_rec t_rec;
  5  begin
  6    OPEN v_rc FOR p_query;
  7    LOOP
  8      FETCH v_rc INTO v_rec;
  9      EXIT WHEN v_rc%NOTFOUND;
10      DBMS_OUTPUT.PUT_LINE('ID: '||v_rec.id||' NAME: '||v_rec.name);
11    END LOOP;
12    CLOSE v_rc;
13* end;
SQL> /
Procedure created.Within this procedure, you will see that we have to provide a structure for the returned data to go into. This means we have to be aware of what data we expect to be returned from our cursor (there are methods for doing it completely dynamically using the DBMS_SQL package but that's a little more complex for you as a newbie). So, our procedure expects the query to return a number and a string. It then opens the cursor and loops through it, exiting the loop when no more records are found and then closing the cursor when done. For each row we find we can do what we like with the data; in my example it is outputting the information to the databases output buffer. It is then up to something else to read that buffer and display the contents.
For this I will use SQL*Plus again.
To tell SQL*Plus to output any contents that appear in the database output buffer, we issue the following command..
SQL> set serveroutput onIf we don't do this then the output will seemingly disappear into oblivion.
So, now we've switched on the output we can execute our procedure.
Firstly, let's execute it to fetch the Employee numbers and names from the EMP table..
SQL> exec proc_exec_query('select empno, ename from emp');
ID: 7369 NAME: SMITH
ID: 7499 NAME: ALLEN
ID: 7521 NAME: WARD
ID: 7566 NAME: JONES
ID: 7654 NAME: MARTIN
ID: 7698 NAME: BLAKE
ID: 7782 NAME: CLARK
ID: 7788 NAME: SCOTT
ID: 7839 NAME: KING
ID: 7844 NAME: TURNER
ID: 7876 NAME: ADAMS
ID: 7900 NAME: JAMES
ID: 7902 NAME: FORD
ID: 7934 NAME: MILLER
PL/SQL procedure successfully completed.Now let's execute the same procedure to fetch the Department number and names from the DEPT table..
SQL> exec proc_exec_query('select deptno, dname from dept');
ID: 10 NAME: ACCOUNTING
ID: 20 NAME: RESEARCH
ID: 30 NAME: SALES
ID: 40 NAME: OPERATIONS
PL/SQL procedure successfully completed.
SQL>So that's just a couple of ways of doing it, and should help to get you started.
;)