How to do a Full Outer Join using old style Oracle syntax

Question

I have two tables with the same columns, Item Code and Qty, for each Table:

TABLE A                    TABLE B
--------------             -------------
X    2                      X   1
Y    1                      S   2
Z    5                      Z   5

The result that I am aiming to get is something like this:

Table C
---------------
X  2  1
Y  1  0
S  0  2

I only need the items where qty differs in both tables (including the nulls which should be shown as zeroes.

Note: I am using Oracle8 so I can't use the ANSI FULL OUTER JOIN.

Answer 1

Edit, Since the question is specific to Oracle 8 which does not use ANSI syntax, the following should work:

select col1, 
  nvl(a_col2, 0) as a_col2, 
  nvl(b_col2, 0) as b_col2
from 
( 
  select a.col1, a.col2 as a_col2, b.col2 as b_col2 
  from TableA a, TableB b
  where a.col1 = b.col1(+)
  union
  select b.col1, a.col2 as a_col2, b.col2 as b_col2 
  from TableA a, TableB b
  where a.col1(+) = b.col1 
)      
where a_col2 <> b_col2
  or (a_col2 is null or b_col2 is null)

See SQL Fiddle with Demo . This will return:

| COL1 | A_COL2 | B_COL2 |
--------------------------
|    S |      0 |      2 |
|    X |      2 |      1 |
|    Y |      1 |      0 |

If you are using a version of Oracle that supports ANSI syntax then you can use the following FULL OUTER JOIN :

select 
  coalesce(a.col1, b.col1) col1, 
  coalesce(a.col2, 0) a_col2, 
  coalesce(b.col2, 0) b_col2
from tablea a
full outer join tableb b
  on a.col1 = b.col1
where a.col2 <> b.col2
  or (a.col2 is null or b.col2 is null);

See SQL Fiddle with Demo

Answer 2

Another writing of the query which should work in 8 and (probably earlier versions).

It uses neither FULL JOIN not the horrible (+) syntax for joins so it should work even when an upgrade deprecates it.

Assuming that there are no Nulls already on the tables, you won't need COALESCE() or NVL() either:

SELECT  a.col1, 
        a.col2 AS a_col2, 
        b.col2 AS b_col2
FROM    TableA a, TableB b
WHERE   a.col1 = b.col1
  AND ( a.col2 <> b.col2
     OR a.col2 IS NULL
     OR b.col2 IS NULL
      )

UNION ALL

SELECT  col1, col2, 0
FROM    TableA a
WHERE   NOT EXISTS
        ( SELECT  *
          FROM    TableB b
          WHERE   a.col1 = b.col1
        )

UNION ALL

SELECT  col1, 0, col2
FROM    TableB b
WHERE   NOT EXISTS
        ( SELECT  *
          FROM    TableA a 
          WHERE   a.col1 = b.col1
        ) ; 

Tests at SQL-Fiddle

Answer 3

select code, nvl(a.qty,0) a, nvl(b.qty,0) b
from tableA a full join tableB b using(code)
where decode(a.qty, b.qty, 0) is null

fiddle

Answer 4

Another option:

select
  full_list.item_code,
  nvl(table_a.qty,0) table_a_qty,
  nvl(table_b.qty,0) table_b_qty
from
  (select item_code from table_a
   union
   select item_code from table_b) full_list,
  table_a,
  table_b
where
  full_list.item_code = table_a.item_code(+) and
  full_list.item_code = table_b.item_code(+)

Answer 5

The following query should work just right:

SELECT * FROM (
  SELECT nvl(a.c1, b.c2), nvl(a.col1, 0) qty1, nvl(b.col2, 0) qty2 FROM a FULL OUTER JOIN b ON a.c1 = b.c2
) where qty1 != qty2;

http://sqlfiddle.com/#!4/d37ff/5/0