Compare Pre-Post tables in oracle sql without hardcoding -

i took pre-image/post-image of table before , after ran batchjob.

pre_table

id|name  |phone    |score 1 |john  |145678   |10 2 |ptr   |23456789 |20 3 |sarah |34567890 |30 4 |mary  |45678901 |40 

post_table

id|name  |phone    |score 1 |john  |12345678 |10 2 |peter |23456789 |22 3 |sarah |34567890 |33 4 |mary  |45678901 |40 

how compare , extract modified fields , present them follows:

desired output

id|modifiedcolumn|modifiedval|prevval 1 |phone         |12345678   |145678    2 |name          |peter      |ptr 2 |score         |22         |20 3 |score         |33         |30 

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so far, can modified rows using

select * post_table minus select * pre_table 

which gives me

id|name  |phone    |score 1 |john  |12345678 |10 2 |peter |23456789 |22 3 |sarah |34567890 |33 

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i thinking of using all_tab_columns iterate fields in table

select column_name all_tab_columns table_name ='pre_table'; 

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i have written partial pl-sql procedure, got stuck when wanted compare column names.

procedure diff cursor post_cur (select * post_table minus select * pre_table);  cursor pre_cur (select * pre_table);  cursor columns_cur select column_name all_tab_columns table_name ='post_table';  begin   r in post_cur loop       p in pre_cur loop           if (r.id=p.id)               f in columns_cur loop                      dbms_output.put_line('id:'||r.id||'_'||f.column_name);                   --compare f.column_name.. stuck here!!                    --if (r.[f.column_name] <>p.[f.column_name] )                      --dbms_output.put_line('id:'||r.id||'_'||f.column_name||'_'||r.[f.column_name]||'_'||p.[f.column_name]);                   --end if;               end loop;           end if;       end loop;   end loop;  end diff; 

how table results dynamically without hardcoding table column names? open use pl-sql or else works. tia.

i think can results looking using following sql:

--phone select a.id, 'phone' modifiedcolumn, b.phone modifiedval, a.phone prevval pre_table inner join post_table b on a.id = b.id , coalesce(a.phone,'-') <> coalesce(b.phone,'-')  --name union select a.id, 'name' modifiedcolumn, b.phone modifiedval, a.phone prevval pre_table inner join post_table b on a.id = b.id , coalesce(a.name,'-') <> coalesce(b.name,'-')  --score union select a.id, 'score' modifiedcolumn, b.phone modifiedval, a.phone prevval pre_table inner join post_table b on a.id = b.id , coalesce(a.score,'0') <> coalesce(b.score,'0')