How to devide the set of records into groups in SQL itself.

Question

Hi , i am using 10.2.4.0 of oracle.
I am having one requirement, in which i have to devide the set of records into certain groups , so that they can be executed partly but not in one run.
So in the 'SELECT' clause itself i want to asssign particular value (may be 1 )to first 50000 records then another value(may be 2) to next 10000, like wise. And again the total count of records will also varry time to time , if the total count of record set is less than 10000 , then it should only assign '1' to all the records. i will set the group values (1,2,3...) as another column itself.
Can you please let me know if this can be done in SQL without going for PLSQL?

Answer 1

Hi,
That's called a Pagination Query , and here's one way to do it:
WITH     got_grp          AS
     SELECT     x.*
     ,     CEIL ( ROW_NUMBER () OVER (ORDER BY  x_id) 
               / 50000
               )          AS grp
     FROM     table_x  x
--     WHERE     ...          -- If you need any filtering, put it here
SELECT     *               -- Or list the columns you want
FROM     got_grp
WHERE     grp     = 1
;ROW_NUMBER () OVER (ORDER BY x_id)     assigns unique integers 1, 2, 3, ... to all all rows, in the same order as x_id (even if x_id is not unique).
CEIL (ROW_NUMBER () OVER (ORDER BY x_id) / 50000)     maps the 1st 50,000 of those numbers to 1, the 2nd 50,000 to 2, and so on.
Analytic functions (like ROW_NUMBER) as computed after the WHERE clause is applied, so, to use the results in a WHERE clause, then you need to compute them in a sub-query. If you just want to display the number, and not use it in a WHERE clause, then you don't need a sub-query.
I hope this answers your question.
If not, post a little sample data (CREATE TABLE and INSERT statements, relevant columns only) for all the tables involved, and the results you want from that data.
In the case of a DML operation (such as UPDATE) the sample data should show what the tables are like before the DML, and the results will be the contents of the changed table(s) after the DML.
Explain, using specific examples, how you get those results from that data.
Always say what version of Oracle you're using.
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