Limit number of rows returned in Toad

Question

Hi,
I use toad to query a database, in fact, its a data warehouse and each time my query returns a huge number of rows and I have to wait for quite some time. Is there a way of getting only a few rows at a time. I mean, I want to see the complete data returned by in a piecemeal manner, say it fetches me the first 30 rows and I keep seeing this data while it keeps getting the next 30.
Any suggestions?
Thanks in advance,
Rajesh

Answer 1

The first query will give you a random set of 100 rows from your table. There is no such thing as the "first 100 rows" without an order by in the inner query. The secons query will return nothing.
SQL> SELECT * FROM (
  2  SELECT indv_id FROM indv_t)
  3* WHERE rownum > 100 and rownum < 200;
no rows selectedA close approximation of this query that does return rows is:
SQL> SELECT * FROM (
  2  SELECT indv_id,rownum rn FROM indv_t)
  3* WHERE rn > 100 and rn < 200;
INDV_ID           RN
1040             101
1057             102
1073             103
2055             197
2063             198
2071             199
99 rows selected.The only correct, repeatable, efficient way to page data is something like:
SELECT * FROM
   SELECT *, rownum rn FROM
      your query here WITH AN ORDER BY
   WHERE rn <= :max_value
WHERE rn >= :min_valueOracle will not guarantee that the same query will return the rows in the same order for every execution without an ORDER BY clause. There are dozens of factors that can influence the query path chosen by the optimizer, and therefore the order of the rows returned. As the optimizer gets more complex (and smarter?), and Oracle adds new acces paths, I xan only assume that the number of factors influencing the access path will continue to grow.
In short, if you want to talk about first and last rows, you need to sort them first.
TTFn
John