Question

I want an approach/code snippet to extract column names and the corresponding table name from an oracle query. The queries and consequently the columns and table names change at run time and some of the column names usually are calculated meaning they are wrapped in a function and aliased. I tried different string tokenizing techniques using regexp to separate this out as per the expeted output, but so far, no luck !
Eg:

select mandate_name, investment_sub_team_name,
fn_sum(REG_INV_CMP_AUM) REG_INV_CMP_AUM, 
fn_sum(NON_REG_INV_CMP_AUM) NON_REG_INV_CMP_AUM
from DM_SAI_VALUATIONS_STEP3
where position_interval_type = 'E'
and position_type = 'T'
group by mandate_name, investment_sub_team_name;

I want the output for the columns as:

mandate_name
investment_sub_team_name
fn_sum(REG_INV_CMP_AUM)
fn_sum(NON_REG_INV_CMP_AUM)

Note above: I want the columns with the function and not the alias

I want the output for the table name as: DM_SAI_VALUATIONS_STEP3 against all the columns that I listed above

I cannot edit the queries as they are part of an xml output. So, i cannot change the alias. The second point is to just extract the table name from the query. Please consider the fact that nothing can be hard coded like position of the string token etc as the queries containing the columns and the table would be different. I am looking for a generic approach to tokenize them. So, against the column output that I expect, i just need the table name as well..Its always going to only one table in the from clause, so extracting that would not be an issue.

Expected output:

Column Name                          Table Name
-----------                          ----------
mandate_name                         DM_SAI_VALUATIONS_STEP3
investment_sub_team_name             DM_SAI_VALUATIONS_STEP3
fn_sum(REG_INV_CMP_AUM)              DM_SAI_VALUATIONS_STEP3
fn_sum(NON_REG_INV_CMP_AUM)          DM_SAI_VALUATIONS_STEP3

Any help pr pointers would be much appreciated.

Answer 1

If you know that the structure of your query strings will not change much, you can do something like this:

set serveroutput on
set termout on
clear
declare
  v_str varchar2(500) := 'select mandate_name, investment_sub_team_name,
fn_sum(REG_INV_CMP_AUM) REG_INV_CMP_AUM, 
fn_sum(NON_REG_INV_CMP_AUM) NON_REG_INV_CMP_AUM
from DM_SAI_VALUATIONS_STEP3
where position_interval_type = ''E''
and position_type = ''T''
group by mandate_name, investment_sub_team_name;';
  v_tmp varchar2(500);
  v_cols varchar2(500);
  v_table varchar2(500);
begin
  v_tmp := replace( v_str, 'select ','');
  v_tmp := substr( v_tmp, 1, instr(v_tmp, 'where')-1);

  dbms_output.put_line('original query: '||v_str);  

  v_cols := substr (v_tmp, 1, instr(v_tmp, 'from')-1);
  dbms_output.put_line('column names: '||v_cols);


  v_table := substr(v_tmp, instr(v_tmp, 'from ')+4, 500);
  dbms_output.put_line('table name: '||v_table);
end;