How to get top three count(trap_text)

Question

Hi,
Wrote file afiedt.buf
1 select gasid,count(trap_text) from kr_reported_alerts alerts
2 where exists (select * from kr_reported_alerts where gasid=alerts.gasid)
3* group by gasid
SQL> /
GASID COUNT(TRAP_TEXT)
HUNTER_TEST00001 2
HUNTER_TEST00003 83
HUNTER_TEST00011 4
HUNTER_TEST00024 12918
here i want to get top three count(trap_text) one 12918 and another is 83 and another is 4
Message was edited by:
user517983
Message was edited by:
user517983

Answer 1

Note that the subquery within subquery is completely redundant; for every row in the outer query there is bound to be at least one row (the same row) in the correlated subquery. There could be more, of course (depending on the structure of kr_reported_alerts).
SELECT *
FROM (select gasid,count(trap_text) from kr_reported_alerts alerts
/* NOT NEEDED -- where exists (select * from kr_reported_alerts where gasid=alerts.gasid) */
group by gasid)
WHERE rownum < 4;
The results from this may be different from either RANK or DENSE_RANK. Consider this data set; rows
Gasid Count Rank Dense-Rank Rownum
G1    100   1         1      1
G2     90   2         2      2
G3     90   2         2      3
G4     90   2         2      4
G5     80   5         3      5
G6     80   5         3      6You can see that each will give a different result:
Rank: G1 through G4
Dense Rank: G1 through G5
Rownum: G1 through G3 (in fact the ROWNUM solution could give you any one of G3, G4 or G5 at random)
Regards Nigel