SQL Statement for Reconciliation

Question

Given the schema below:

create table TBL1 (ID varchar2(100) primary key not null, MATCH_CRITERIA varchar2(100));
create table TBL2 (ID varchar2(100) primary key not null, MATCH_CRITERIA varchar2(100));
create table TBL_RESULT (ID varchar2(100) primary key not null, TBL1_ID varchar2(100), TBL2_ID varchar2(100));

create unique index UK_TBL_RESULT_TBL1_ID on TBL_RESULT(TBL1_ID);
create unique index UK_TBL_RESULT_TBL2_ID on TBL_RESULT(TBL2_ID);

create sequence SEQ_TBL_RESULT;

insert into TBL1 VALUES('1', '1');
insert into TBL1 VALUES('2', '1');
insert into TBL1 VALUES('3', '1');

insert into TBL2 VALUES('4', '1');
insert into TBL2 VALUES('5', '1');
insert into TBL2 VALUES('6', '1');

I need an SQL statement that will produce the result by reconciling equal MATCH_CRITERIA from TBL1 and TBL2.

The following would work given that the UNIQUE constraint is not present. However, we need the unique constraints in our application.

insert into TBL_RESULT (ID, TBL1_ID, TBL2_ID)
select SEQ_TBL_RESULT.nextval, TBL1.ID, TBL2.ID
from TBl1, TBL2
where TBL1.MATCH_CRITERIA = TBL2.MATCH_CRITERIA;

Example output of TBL_RESULT

| ID  |  TBL1_ID | TBL2_ID |
| '1' |  '1'     |    '5'  |
| '2' |  '2'     |    '4'  |
| '3' |  '3'     |    '6'  |

Note: it doesn't matter if '1' is matched with '4' or '6'. As long as the MATCH_CRITERIA from both tables are equal and the resulting table has unique TBL1_ID and TBL2_ID.

Note that we are inserting a million records from TBL1 and another million records from TBL2. Thus, sequential insert using PL/SQL is not acceptable unless it can run really fast (less than 15 minutes).

Answer 1

how about this:

  INSERT INTO TBL_RESULT (ID, TBL1_ID, TBL2_ID) 
  SELECT seq_tbl_result.nextval,t1.id,t2.id 
  FROM
  (SELECT t1.match_criteria,t1.id, row_number() OVER (PARTITION BY t1.match_criteria ORDER BY t1.id) rn 
   FROM tbl1 t1) t1,  
  (SELECT t2.match_criteria,t2.id, row_number() OVER (PARTITION BY t2.match_criteria ORDER BY t2.id) rn 
   FROM tbl2 t2) t2
  WHERE t1.match_criteria=t2.match_criteria AND t1.rn=t2.rn

Note: It assumes that there are an equal number of rows in each matching set in both tables.

Answer 2

What about something like this:

insert into TBL_RESULT (ID, TBL1_ID, TBL2_ID)
select SEQ_TBL_RESULT.nextval, TBL1.ID, TBL2.ID 
from TBl1, TBL2
where TBL1.MATCH_CRITERIA = TBL2.MATCH_CRITERIA
AND (NOT EXISTS (SELECT 1 FROM TBL_RESULT WHERE TBL1_ID = TBL1.ID) OR NOT EXISTS(SELECT 1 FROM TBL_RESULT WHERE TBL2_ID = TBL2.id))

This should prevent violation of your unique constraints.