Selecting using a field that stores a column_name to be used in the where

Question

I have a table REPORTING_CRITERIA with fields and field values:
gl_criteria1 = 'cc.segment5'
from_value1= '1123'
to_value1= '1130'
gl_criteria2 = 'cc.segment5'
from_value2 = '1140'
to_value2 = '1150'
I am trying to run a select where I pull records where the actual field name stored in gl_criteria1 and gl_criteria2 is used in the where clause.
ie.
select bal.gl_balance, account_code
from gl_balances bal, accounts cc, reporting_criteria crit
where crit.report_name ='BUDGET'
and crit.gl_criteria1 between crit.from_value1 and crit.to_value1
What I want is to have the where read like:
where crit.report_name ='BUDGET'
and cc.segment5 between crit.from_value1 and crit.to_value1
Thus cc.segment5 is the value stored in the reporting_criteria table in the gl_criteria1 field but it is an actual db column to be used in my select.
How can I get this query to work so that the contents of gl_criteria1 field are actually read like a column name in my where?
Edited by: ajgolden87 on Nov 8, 2012 11:10 AM

Answer 1

Hi,
You should know the column names of the table you are quering. If so you can make queries like this:
with CC as
select 1 id, 1123 segment5 from dual union all
select 2 id, 1124 segment5 from dual union all
select 3 id, 1125 segment5 from dual union all
select 4 id, 1126 segment5 from dual union all
select 5 id, 1127 segment5 from dual union all
select 6 id, 1128 segment5 from dual union all
select 7 id, 1129 segment5 from dual union all
select 8 id, 1130 segment5 from dual union all
select 9 id, 1131 segment5 from dual union all
select 10 id, 1132 segment5 from dual
,REPORTING_CRITERIA  AS
SELECT
  'SEGMENT5'        GL_CRITERRIA_1
  ,'1123'           FROM_VALUE_1
  ,'1130'           TO_VALUE_1
  ,'ID'             GL_CRITERRIA_2
  ,'4'              FROM_VALUE_2
  ,'7'              TO_VALUE_2
FROM
  DUAL
SELECT
  cc.*
FROM
  CC
  ,REPORTING_CRITERIA
WHERE
  GL_CRITERRIA_1 IS NULL
  OR CASE WHEN GL_CRITERRIA_1 = 'SEGMENT5' THEN SEGMENT5
          WHEN GL_CRITERRIA_1 = 'ID' THEN ID
          ELSE NULL END BETWEEN FROM_VALUE_1 AND TO_VALUE_1
  ) AND
  GL_CRITERRIA_2 IS NULL
  OR CASE WHEN GL_CRITERRIA_2 = 'SEGMENT5' THEN SEGMENT5
          WHEN GL_CRITERRIA_2 = 'ID' THEN ID
          ELSE NULL END BETWEEN FROM_VALUE_2 AND TO_VALUE_2
ID SEGMENT5
4     1126
5     1127
6     1128
7     1129 Regards,
Peter