Creating a view based on history tables

Question

I want to create a SQL view based on a database with history tables.

Which is the best solution (fast and efficient) to do that. I have not created the application and I cannot update the database tables. I can only create views.

Here is the context:

My application manages contracts. A contract has general information and is linked to contacts, legal references and portfolios. When an update is done, a new line is added in the history tables (new ID_HIST). If an update is done on the contacts, legal references or portfolios, a new line is equally added in the table contract_HIST (with the same ID_HIST).

My purpose is the creation of a view to display the updates done on a row (ID HIST) compared to the previous ID HIST like:

Thus for each new update (for a specific date wanted, given thanks to ID HIST), we can see if the general information, the contacts, the legal references or/and the portfolios have been updated.

Here below the structure of the database:

Here in the table one or several Portfolios can be assigned to a contract for a same update.

For information: if for example during a new update, the contacts have been deleted for a contract, a new line (with a new ID_HIST) is added in contract_hist for this contract BUT no new line is added in the table contact_hist. It's the same for legal reference and portfolios.

Here the view should display:

Here the scripts for the database for testing:

    --------------------------------------------------------  
-- DDL for Table CONTACT_HIST  
--------------------------------------------------------  

  CREATE TABLE "CONTACT_HIST"   
   (     "ID_HIST" NUMBER,   
     "ID_CONTRAT" NUMBER,   
     "NAME_CONTACT" VARCHAR2(20 BYTE)  
   ) SEGMENT CREATION IMMEDIATE   
  PCTFREE 10 PCTUSED 40 INITRANS 1 MAXTRANS 255   
 NOCOMPRESS LOGGING  
  STORAGE(INITIAL 65536 NEXT 1048576 MINEXTENTS 1 MAXEXTENTS 2147483645  
  PCTINCREASE 0 FREELISTS 1 FREELIST GROUPS 1  
  BUFFER_POOL DEFAULT FLASH_CACHE DEFAULT CELL_FLASH_CACHE DEFAULT)  
  TABLESPACE "RAM" ;  
REM INSERTING into BO.CONTACT_HIST  
SET DEFINE OFF;  
Insert into BO.CONTACT_HIST (ID_HIST,ID_CONTRAT,NAME_CONTACT) values (1,1,'Bernard');  
Insert into BO.CONTACT_HIST (ID_HIST,ID_CONTRAT,NAME_CONTACT) values (1,1,'Jean');  
Insert into BO.CONTACT_HIST (ID_HIST,ID_CONTRAT,NAME_CONTACT) values (2,1,'Nicolas');  
Insert into BO.CONTACT_HIST (ID_HIST,ID_CONTRAT,NAME_CONTACT) values (2,1,'Jean');  
Insert into BO.CONTACT_HIST (ID_HIST,ID_CONTRAT,NAME_CONTACT) values (3,2,'Nicolas');  
Insert into BO.CONTACT_HIST (ID_HIST,ID_CONTRAT,NAME_CONTACT) values (5,2,'Nicolas');  

--------------------------------------------------------  
-- DDL for Table CONTRAT_HIST  
--------------------------------------------------------  

  CREATE TABLE "BO"."CONTRAT_HIST"   
   (     "ID_HIST" NUMBER,   
     "DATE_CREATION" DATE,   
     "ID_CONTRAT" NUMBER,   
     "TITRE_CONTRAT" VARCHAR2(250 BYTE),   
     "DESCRIPTION" VARCHAR2(250 BYTE),   
     "BUDGET" NUMBER  
   ) SEGMENT CREATION IMMEDIATE   
  PCTFREE 10 PCTUSED 40 INITRANS 1 MAXTRANS 255   
 NOCOMPRESS LOGGING  
  STORAGE(INITIAL 65536 NEXT 1048576 MINEXTENTS 1 MAXEXTENTS 2147483645  
  PCTINCREASE 0 FREELISTS 1 FREELIST GROUPS 1  
  BUFFER_POOL DEFAULT FLASH_CACHE DEFAULT CELL_FLASH_CACHE DEFAULT)  
  TABLESPACE "RAM" ;  
REM INSERTING into BO.CONTRAT_HIST  
SET DEFINE OFF;  
Insert into BO.CONTRAT_HIST (ID_HIST,DATE_CREATION,ID_CONTRAT,TITRE_CONTRAT,DESCRIPTION,BUDGET) values (1,to_date('01-JAN-15','DD-MON-RR'),1,'Contrat 1 ','Contrat Informatique ',20000);  
Insert into BO.CONTRAT_HIST (ID_HIST,DATE_CREATION,ID_CONTRAT,TITRE_CONTRAT,DESCRIPTION,BUDGET) values (2,to_date('15-JAN-15','DD-MON-RR'),1,'Contrat 1 ','Contrat Informatique ',50000);  
Insert into BO.CONTRAT_HIST (ID_HIST,DATE_CREATION,ID_CONTRAT,TITRE_CONTRAT,DESCRIPTION,BUDGET) values (3,to_date('02-FEB-15','DD-MON-RR'),2,'Contrat 2 ','Contrat Santé ',10000);  
Insert into BO.CONTRAT_HIST (ID_HIST,DATE_CREATION,ID_CONTRAT,TITRE_CONTRAT,DESCRIPTION,BUDGET) values (4,to_date('01-MAR-15','DD-MON-RR'),2,'Contrat 2 ','Contrat Consommateur ',30000);  
Insert into BO.CONTRAT_HIST (ID_HIST,DATE_CREATION,ID_CONTRAT,TITRE_CONTRAT,DESCRIPTION,BUDGET) values (5,to_date('01-JUL-15','DD-MON-RR'),1,'Contrat 1 ','Contrat Informatique ',50000);  
--------------------------------------------------------  
-- DDL for Index CONTRAT_HIST_PK  
--------------------------------------------------------  

  CREATE UNIQUE INDEX "BO"."CONTRAT_HIST_PK" ON "BO"."CONTRAT_HIST" ("ID_HIST")   
  PCTFREE 10 INITRANS 2 MAXTRANS 255 COMPUTE STATISTICS   
  STORAGE(INITIAL 65536 NEXT 1048576 MINEXTENTS 1 MAXEXTENTS 2147483645  
  PCTINCREASE 0 FREELISTS 1 FREELIST GROUPS 1  
  BUFFER_POOL DEFAULT FLASH_CACHE DEFAULT CELL_FLASH_CACHE DEFAULT)  
  TABLESPACE "RAM" ;  
--------------------------------------------------------  
-- Constraints for Table CONTRAT_HIST  
--------------------------------------------------------  

  ALTER TABLE "BO"."CONTRAT_HIST" ADD CONSTRAINT "CONTRAT_HIST_PK" PRIMARY KEY ("ID_HIST")  
  USING INDEX PCTFREE 10 INITRANS 2 MAXTRANS 255 COMPUTE STATISTICS   
  STORAGE(INITIAL 65536 NEXT 1048576 MINEXTENTS 1 MAXEXTENTS 2147483645  
  PCTINCREASE 0 FREELISTS 1 FREELIST GROUPS 1  
  BUFFER_POOL DEFAULT FLASH_CACHE DEFAULT CELL_FLASH_CACHE DEFAULT)  
  TABLESPACE "RAM"  ENABLE;  
  ALTER TABLE "BO"."CONTRAT_HIST" MODIFY ("ID_HIST" NOT NULL ENABLE);  

--------------------------------------------------------  
-- DDL for Table LEGAL_REFERENCE_HIST  
--------------------------------------------------------  

  CREATE TABLE "BO"."LEGAL_REFERENCE_HIST"   
   (     "ID_HIST" NUMBER,   
     "ID_CONTRAT" NUMBER,   
     "LEG_REF_NAME" VARCHAR2(250 BYTE)  
   ) SEGMENT CREATION IMMEDIATE   
  PCTFREE 10 PCTUSED 40 INITRANS 1 MAXTRANS 255   
 NOCOMPRESS LOGGING  
  STORAGE(INITIAL 65536 NEXT 1048576 MINEXTENTS 1 MAXEXTENTS 2147483645  
  PCTINCREASE 0 FREELISTS 1 FREELIST GROUPS 1  
  BUFFER_POOL DEFAULT FLASH_CACHE DEFAULT CELL_FLASH_CACHE DEFAULT)  
  TABLESPACE "RAM" ;  
REM INSERTING into BO.LEGAL_REFERENCE_HIST  
SET DEFINE OFF;  
Insert into BO.LEGAL_REFERENCE_HIST (ID_HIST,ID_CONTRAT,LEG_REF_NAME) values (1,1,'45 - Technologies et Systeme d''Information');  
Insert into BO.LEGAL_REFERENCE_HIST (ID_HIST,ID_CONTRAT,LEG_REF_NAME) values (2,2,'105 - Consommateur et Santé');  
Insert into BO.LEGAL_REFERENCE_HIST (ID_HIST,ID_CONTRAT,LEG_REF_NAME) values (5,1,'27 - Services');  

--------------------------------------------------------  
-- DDL for Table PORTFOLIO_HIST  
--------------------------------------------------------  

  CREATE TABLE "BO"."PORTFOLIO_HIST"   
   (     "ID_HIST" NUMBER,   
     "ID_CONTRAT" NUMBER,   
     "PORTFOLIO_ID" NUMBER,   
     "PORTFOLIO_NAME" VARCHAR2(250 BYTE),   
     "PORTFOLIO_VALUE" NUMBER  
   ) SEGMENT CREATION IMMEDIATE   
  PCTFREE 10 PCTUSED 40 INITRANS 1 MAXTRANS 255   
 NOCOMPRESS LOGGING  
  STORAGE(INITIAL 65536 NEXT 1048576 MINEXTENTS 1 MAXEXTENTS 2147483645  
  PCTINCREASE 0 FREELISTS 1 FREELIST GROUPS 1  
  BUFFER_POOL DEFAULT FLASH_CACHE DEFAULT CELL_FLASH_CACHE DEFAULT)  
  TABLESPACE "RAM" ;  
REM INSERTING into BO.PORTFOLIO_HIST  
SET DEFINE OFF;  
Insert into BO.PORTFOLIO_HIST (ID_HIST,ID_CONTRAT,PORTFOLIO_ID,PORTFOLIO_NAME,PORTFOLIO_VALUE) values (2,1,1,'Portfolio 1',5000);  
Insert into BO.PORTFOLIO_HIST (ID_HIST,ID_CONTRAT,PORTFOLIO_ID,PORTFOLIO_NAME,PORTFOLIO_VALUE) values (2,1,2,'Portfolio 2',7000);  
Insert into BO.PORTFOLIO_HIST (ID_HIST,ID_CONTRAT,PORTFOLIO_ID,PORTFOLIO_NAME,PORTFOLIO_VALUE) values (4,2,1,'Portfolio 1',2000);  
Insert into BO.PORTFOLIO_HIST (ID_HIST,ID_CONTRAT,PORTFOLIO_ID,PORTFOLIO_NAME,PORTFOLIO_VALUE) values (4,2,2,'Portfolio 2',8000);  
commit;  

Answer 1

here we go:

first: create a stored function (or a function in a package) like this:

create or replace function test_history(i_contract_id  in number,
                                        i_date_created in date,
                                        i_type         in varchar2)
  return varchar2 is
  l_sql    varchar2(1000);
  l_result number;
begin
  l_sql := 'select 1 from test_history_tb where id_contract = :1 and date_creation = :2 and ' ||
           i_type || ' = :3 and rownum = 1';
  execute immediate l_sql
    into l_result
    using i_contract_id, i_date_created, 'update';

  return('update');

exception
  when no_data_found then
    return('no_update');
end;

second: create your query based on the function:

create view xxx as

select id_contract, date_creation,
       test_history(a.id_contract, a.date_creation, 'general_info') general_info,
       test_history(a.id_contract, a.date_creation, 'contract') contract,
       test_history(a.id_contract, a.date_creation, 'legal') legal,
       test_history(a.id_contract, a.date_creation, 'portfolio') portfolio
from test_history_tb a
group by a.id_contract, a.date_creation;

this solution is not that fast, because for each row we have a function call. but if you filter the data with a where-clause it would be a alternative.

the example data in the table:

... and here is how the query on the view looks like: