Question

Possible Duplicate:
How do I limit the number of rows returned by an Oracle query after ordering?

I am using just like below query:

SELECT url, title, metadesc FROM (
        SELECT url,title, metadesc, rownum rn FROM (
                SELECT url, title, metadesc FROM web
            )
            WHERE rownum <= 60
    )
    WHERE rn > 50

it works fine for single table but if do join in my main query
i.e

SELECT name, id, url, title, metadesc
FROM web, emp

then it gives me error:

java.sql.SQLException: ORA-00918: column ambiguously defined

Answer 1

Use either aliases:

SELECT e.name, e.id, w.url, w.title, w.metadesc
  FROM web w
  JOIN emp e ON w.xx = e.yy

Or full table names (more verbose):

SELECT emp .name, emp .id, web.url, web.title, web.metadesc
  FROM web
  JOIN emp ON web.xx = emp .yy

If a subquery returns two columns with the same name, you can’t do a SELECT *:

SQL> SELECT * FROM (
  2     SELECT d1.dummy, d2.dummy
  3       FROM dual d1, dual d2
  4  );

ERROR at line 1:
ORA-00918: column ambiguously defined

In that case use different column names in the subquery with aliases:

SQL> SELECT * FROM (
  2     SELECT d1.dummy dummy_d1, d2.dummy dummy_d2
  3       FROM dual d1, dual d2
  4  );

D D
- -
X X