What is wrong in this "order by", "group by" sql?

Question

I have got this SQL, it yields ORA-00920 Invalid relational operator error, what is wrong and how can I fix this?

select * from my_tab where (a,b,c,t) in
 ( select a,b,c, max(t) as t from my_tab where foo<>'bar'
   group by a,b,c
   order by t
 ) and rownum between 20 and 30

(also tried rownum>20 and rownum<30 )

DDL:

create table my_tab
(a number,
 b number,
 c number,
 t  date,
 foo varchar2(20),
 buzz varchar2(2000)
);

There is no index in the table.

I want to read the whole table actually, but since there are many rows, I want to process in chunks. I cannot add column to the table (for example a unique id or a counter to hold the progress).

Answer 1

There are a couple of problems here:

1. First, the invalid comparison operator is caused by the construct (a,b,c,t) IN (...subquery...) . You'll need to do an INNER JOIN of the subquery.
2. ROWNUM BETWEEN 20 AND 30 will never return any data. ROWNUM is not generated until a row is emitted from the query, so the first row emitted from the query always has ROWNUM = 1. The problem here is that you're waiting for a row with ROWNUM = 20 to be emitted - but none of the preceding rows have ever been generated. Thus, no data. The workaround for this is to pull all the rows in a subquery, then look for the appropriate rows in an outer query.

Put together, we get:

WITH cteData AS (SELECT A, B, C, MAX(T) AS MAX_T
                   FROM MY_TAB
                   WHERE FOO <> 'bar'
                   GROUP BY A, B, C
                   ORDER BY MAX(T))
SELECT *
  FROM (SELECT mt.*, ROWNUM AS RN
          FROM MY_TAB mt
          INNER JOIN cteData d
          ON d.A = mt.A AND
             d.B = mt.B AND
             d.C = mt.C AND
             d.MAX_T = mt.T) sq
  WHERE sq.RN BETWEEN 20 AND 30

Answer 2

Either of these will work:

select * from my_tab
where (a,b,c,t) in
 ( select a,b,c,t from 
    ( select a,b,c, max(t) as t, row_number() over ( order by max(t)) rn
      from my_tab
      where foo<>'bar'
      group by a,b,c
    )
   where rn between 20 and 30
) ;

(in 12c only...)

select * from my_tab
where (a,b,c,t) in
    ( select a,b,c, max(t) as t
      from my_tab
      where foo<>'bar'
      group by a,b,c
      offset 19 rows
      fetch next 11 rows only  -- should give you rows 20 thru 30, a weird window of 11 rows
    );

Note:

I want to read the whole table actually, but since there are many rows, I want to process in chunks.

If you try to do it this way, you'll be re-reading the whole table for every chunk ! If you post some more details about what you are trying to do (probably a separate question would be appropriate), someone here can probably help you avoid that with a different approach.

Answer 3

The solution is mentioned in the comments, but just to summarize: Two things to be done here. 1) Add t to the where condition 2) Remove the order by in the subquery:

SELECT * 
FROM my_tab 
WHERE (a,b,c,t) IN
         (select a,b,c, max(t) as t from my_tab where foo<>'bar'
          group by a,b,c) 
  and rownum between 20 and 30;

Hope this helps.

Answer 4

The problem is that you have 3 values before the in clause and 4 columns coming from the subquery.

This code might help you.

WITH my_tab AS (

    SELECT 'a' AS a,
            'b' AS b,
            'c' AS c,
             1 AS t,
             'bar!' AS foo
    FROM dual 

)
SELECT * FROM (
    SELECT t.*, ROWNUM AS RN FROM my_tab t WHERE ('a','b','c') IN
     ( 
        SELECT a,b,c FROM ( 
            select a,b,c, max(t) as t 
                from my_tab where foo <> 'bar'
            group by a,b,c
          order by t
     )
 )
 ) 
WHERE  RN between 0 and 1

Copy and paste this code into your oracle client and see the result. I think it will work as you expect.

If you want to filter using the t value, the query below might be useful:

 WITH my_tab AS (

    SELECT 'a' AS a,
            'b' AS b,
            'c' AS c,
             1 AS t,
             'bar!' AS foo
    FROM dual 

)
SELECT * FROM (
    SELECT t.*, ROWNUM AS RN FROM my_tab t WHERE ('a','b','c', 1) IN
     ( 
        SELECT a,b,c,t FROM ( 
            select a,b,c, max(t) as t 
                from my_tab where foo <> 'bar'
            group by a,b,c
          order by t
     )
 )
 ) 
WHERE  RN between 0 and 1

This code only works using rownum between 0 and 1 (RN) since there is just one row in my_tab.