How to compare two rows in PL/SQL and retrieve the values?

Question

Hello,
I have two tables which have identical schemas, one table (tbl_store) is used to hold the latest version, and the other table (tbl_store_audit) holds previous versions. When the latest record is updated, it is inserted into the tbl_store_audit table as a revision, and the updated details are used as the latest record.
For example: The latest version is held in tbl_store, however the tbl_store_audit may hold 5 records which are the past records used before changes were made - these are seen as revisions.
I want to be able to compare what has changed between each revision in the tbl_store_audit table. For example: Out of the 10 columns, the change between revision 1 and revision 2 was the size from XL to XXL. The change between revision 3 and revision 4 was the size XS to M and price 4.99 to 10.99, and so on.
Eventually i will create an APEX report that will show the user the revision number and what was changed from and to.
I seen in a previous post i need to note my oracle version: Oracle version 10.2.0.4.0

Answer 1

Hi,
Like suggested already you should give some sample data and output.
Maybe you would like to have something like this:
-- Sample data
-- Note PK is the primairy key of the source table and rev are the revisions
with tbl_store_audit as
select 1 pk, 1 rev , 1 price  , 'XXL' unit_size from dual union all
select 1 pk, 2 rev , 1 price,   'XL'  unit_size from dual union all
select 1 pk, 3 rev , 1.4 price, 'XXL' unit_size from dual union all
select 2 pk, 1 rev , 1.4 price, 'XL'  unit_size from dual union all
select 2 pk, 2 rev , 1.4 price, 'XL'  unit_size from dual union all
select 2 pk, 3 rev , 1.4 price, 'XL'  unit_size from dual union all
select 1 pk, 4 rev , 1 price  , 'XL'  unit_size from dual union all
select 1 pk, 5 rev , 1 price  , 'XL'  unit_size from dual union all
select 3 pk, 1 rev , 1.2 price, 'XL'  unit_size from dual union all
select 3 pk, 2 rev , 1.2 price, 'XXL' unit_size from dual union all
select 4 pk, 1 rev , 1 price  , 'XL'  unit_size from dual
-- end of sample data
,tbl_store_audit_tmp as
select
  pk
  ,rev
  ,'PRICE'          field_name
  ,to_char(price)   field_value
  ,to_char(lag(price,1) over (partition by pk order by rev) ) old_field_value
from
  tbl_store_audit
union all
select
  pk
  ,rev
  ,'UNIT_SIZE'           field_name
  ,to_char(UNIT_SIZE)    field_value
  ,to_char(lag(UNIT_SIZE,1) over (partition by pk order by rev) ) old_field_value
from
  tbl_store_audit
-- include all other fields from the table here with it's own union all select ...
select
from
  tbl_store_audit_tmp
where
  field_value != old_field_value
PK REV FIELD_NAME FIELD_VALUE                              OLD_FIELD_VALUE                       
1   3 PRICE      1.4                                      1                                       
1   4 PRICE      1                                        1.4                                     
1   2 UNIT_SIZE  XL                                       XXL                                     
1   3 UNIT_SIZE  XXL                                      XL                                      
1   4 UNIT_SIZE  XL                                       XXL                                     
3   2 UNIT_SIZE  XXL                                      XL                                      
6 rows selected If you realy want to keep track of all the changes I think it would be better if you make a "after update trigger" on the base table that checks what changed and put that directly in the uadit table.
Regards,
Peter
Edited by: Peter vd Zwan on Aug 16, 2012 8:25 AM