Select records based on first n distinct values of column

Question

I need to write a query in plsql to select records for first 3 distinct values of a single column (below example, ID )and all the rows for next 3 distinct values of the column and so on till the end of count of distinct values of a column.
eg:
ID name age
1 abc 10
1 def 20
2 ghi 10
2 jkl 20
2 mno 60
3 pqr 10
4 rst 10
4 tuv 10
5 vwx 10
6 xyz 10
6 hij 10
7 lmn 10
so on... (till some count)
Result should be
Query 1 should result --->
ID name age
1 abc 10
1 def 20
2 ghi 10
2 jkl 20
2 mno 60
3 pqr 10
query 2 should result -->
4 rst 10
4 tuv 10
5 vwx 10
6 xyz 10
6 hij 10
query 3 should result -->
7 lmn 10
9 .. ..
so on..
How to write a query for this inside a loop.

Answer 1

Hi,
So, one group will consist of the lowest id value, the 2nd lowest and the 3rd lowest, reggardless of how many rows are involved. The next group will consist of the 4th lowest id, the 5th lowest and the 6th lowest. To do that, you need to assign numbers 1, 2, 3, 4, 5, 6, ... to the rows in order by id, with all rows having the same id getting the same number, and without skipping any numbers.
That sounds like a job for the analytic DENSE_RANK function:
WITH     got_grp_id     AS
     SELECT     id, name, age
     ,     CEIL ( DENSE_RANK () OVER (ORDER BY id)
               / 3
               )          AS grp_id
     FROM     table_x
SELECT     id, name, age
FROM     got_grp_id
WHERE     id     = 1     -- or whatever number you want
;If you'd care to post CREATE TABLE and INSERT statements for your sample data, then I could test it.
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