SQL - Query rewrite ?

Question

Hi
I have this query
SELECT a.col1,
a.col2,
a.col3,
a.col4
FROM table1 a
WHERE a.id = (SELECT MAX (id)
FROM table1
WHERE table1.datecol <= p_date AND table1.col5 = p_number);
This is a cursor in a function so p_date and p_number are in parameters.
In the example above table1 contains abot 300 million rows, and the query does 2 scans
of the table1.
Is there anyway to rewrite this SQL statment with one access only ?

Answer 1

Both query will not give the same results
WITH table1 AS
(select 1 id, 1 col1, 1 col2, 1 col3, 1 col4, 1 col5, to_date('01/01/2011','dd/mm/yyyy') datecol from dual
union
select 1 id, 2 col1, 2 col2, 2 col3, 2 col4, 2 col5, to_date('02/01/2011','dd/mm/yyyy') datecol from dual
union
select 3 id, 3 col1, 3 col2, 3 col3, 3 col4, 3 col5, to_date('03/01/2011','dd/mm/yyyy') datecol from dual
union
select 4 id, 4 col1, 4 col2, 4 col3, 4 col4, 3 col5, to_date('03/01/2011','dd/mm/yyyy') datecol from dual
SELECT a.col1,
a.col2,
a.col3,
a.col4
FROM table1 a
WHERE a.id = (SELECT MAX (id)
FROM table1
WHERE table1.datecol <= to_date('03/01/2011','dd/mm/yyyy')
AND table1.col5 = 3);
WITH table1 AS
(select 1 id, 1 col1, 1 col2, 1 col3, 1 col4, 1 col5, to_date('01/01/2011','dd/mm/yyyy') datecol from dual
union
select 1 id, 2 col1, 2 col2, 2 col3, 2 col4, 2 col5, to_date('02/01/2011','dd/mm/yyyy') datecol from dual
union
select 3 id, 3 col1, 3 col2, 3 col3, 3 col4, 3 col5, to_date('03/01/2011','dd/mm/yyyy') datecol from dual
union
select 4 id, 4 col1, 4 col2, 4 col3, 4 col4, 3 col5, to_date('03/01/2011','dd/mm/yyyy') datecol from dual
SELECT * FROM
(SELECT
a.id,
max(a.id) over (partition by a.id order by a.id) maxid,
a.col1,
a.col2,
a.col3,
a.col4,
a.datecol,
a.col5 
FROM table1 a)
WHERE datecol <= to_date('03/01/2011','dd/mm/yyyy')
    AND col5 =3    
    AND id = maxid;Best regards
Mohamed Houri