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formula and placeholder column [message #359826] Tue, 18 November 2008 05:19 Go to next message
nanees
Messages: 4
Registered: October 2008
Junior Member

what is the deferent between formula column and placeholder column in report builder;
and when we use it?????
please help me
icon3.gif  Re: formula and placeholder column [message #360403 is a reply to message #359826] Thu, 20 November 2008 21:05 Go to previous message
arunn
Messages: 52
Registered: September 2008
Location: usa
Member
Hi,
Its nice question,

as per my experience,
Formula column, it use to return the value( atleast u want to mention as RETURN NULL. place holder column is like global variable, using this u can assign the value and get the value in report level.but formula column value is like local variable and also like column, which one scope is inside the group where u created. if u created in report level then scope full report, otherwise its inside any specific group then its scope only inside the group.
The main usage as per my experience.

example:- you are showing the employee details from emp table using the data model ( query ).
requirement : u want to show the department details ( department name, location from dept table based on emp table deptno and dept table dept no ) without data model direct query.

In above case, we are normally use the formula column

v will create 2 formula column for department name and location.

In this case, your query is 2. one is for department and another one is for location. instead of 2 query, using the place holder column u can fetch the both value in one query.

ex:
FUNCTION dept_name IS 
  RETURN VARCHAR2 ( 50 )
BEGIN
  DECLARE
    t_dname VARCHAR2( 50 );
    t_loc   VARCHAR2( 50 );
    CURSOR c_dept IS
      SELECT dname, loc
        FROM dept
       WHERE deptno = :deptno;
  BEGIN
    OPEN c_dept;
    FETCH c_dept INTO t_dname, t_loc;  
    IF c_dept%FOUND THEN
      CLOSE c_dept;
      :place_loc := t_loc;  -- PLACE HOLDER COLUMN
    ELSE   
      CLOSE c_dept;
    END IF;
    RETURN t_dname;
  END;
END; 

In above case, u reduce the one query firing and also save the report executing time and also db performance improve etc...........

i have explained as per my experience. let me know if u have any idea or queries.

take care

arun doss
USA

[EDITED by LF: applied [code] tags]

[Updated on: Fri, 21 November 2008 00:11] by Moderator

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