How to Select Top 100 rows in Oracle?

My requirement is to get each client's latest order, and then get top 100 records.

I wrote one query as below to get latest orders for each client. Internal query works fine. But I don't know how to get first 100 based on the results.

 SELECT * FROM ( SELECT id, client_id, ROW_NUMBER() OVER(PARTITION BY client_id ORDER BY create_time DESC) rn FROM order ) WHERE rn=1

Any ideas? Thanks.

2

6 Answers

Assuming that create_time contains the time the order was created, and you want the 100 clients with the latest orders, you can:

• add the create_time in your innermost query
• order the results of your outer query by the create_time desc
• add an outermost query that filters the first 100 rows using ROWNUM

Query:

 SELECT * FROM ( SELECT * FROM ( SELECT id, client_id, create_time, ROW_NUMBER() OVER(PARTITION BY client_id ORDER BY create_time DESC) rn FROM order ) WHERE rn=1 ORDER BY create_time desc ) WHERE rownum <= 100

UPDATE for Oracle 12c

With release 12.1, Oracle introduced "real" Top-N queries. Using the new FETCH FIRST... syntax, you can also use:

 SELECT * FROM ( SELECT id, client_id, create_time, ROW_NUMBER() OVER(PARTITION BY client_id ORDER BY create_time DESC) rn FROM order ) WHERE rn = 1 ORDER BY create_time desc FETCH FIRST 100 ROWS ONLY)

9

you should use rownum in oracle to do what you seek

where rownum <= 100

see also those answers to help you

limit in oracle

select top in oracle

select top in oracle 2

1

As Moneer Kamal said, you can do that simply:

SELECT id, client_id FROM order
WHERE rownum <= 100
ORDER BY create_time DESC;

Notice that the ordering is done after getting the 100 row. This might be useful for who does not want ordering.

Update:

To use order by with rownum you have to write something like this:

SELECT * from (SELECT id, client_id FROM order ORDER BY create_time DESC) WHERE rownum <= 100;

First 10 customers inserted into db (table customers):

select * from customers where customer_id <=
(select min(customer_id)+10 from customers)
Last 10 customers inserted into db (table customers):
select * from customers where customer_id >=
(select max(customer_id)-10 from customers)

Hope this helps....

1

To select top n rows updated recently

SELECT *
FROM ( SELECT * FROM table ORDER BY UpdateDateTime DESC
)
WHERE ROWNUM < 101;

Try this:

 SELECT *
FROM (SELECT * FROM ( SELECT id, client_id, create_time, ROW_NUMBER() OVER(PARTITION BY client_id ORDER BY create_time DESC) rn FROM order ) WHERE rn=1 ORDER BY create_time desc) alias_name
WHERE rownum <= 100
ORDER BY rownum;

Or TOP:

SELECT TOP 2 * FROM Customers; //But not supported in Oracle

NOTE: I suppose that your internal query is fine. Please share your output of this.

4

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