How to "page" results from a database?

[Andrew Carney]

Hello,

Suppose I need to query a database and the result contains 100K of records. Can someone please show me a code example of how to "page" the result for, say, 1K of records at a time?

[John Simpson]

Hi,

If you are using a relational database and the data is ordered then you can do the paging in the SQL statement, on many DBs anyway.
Something like:

  
select *
from mytable
where key > lastKey
fetch first 1000 rows only
  

The fetch statement controls the number of rows returned. Set lastKey to the key of the last record in the previous page.
There's probably a better way to do it, but that should work.

John

[Andrew Carney]

Hi John,

Interesting solution, the only problem is that they key is not something numeric that I can run on, it's random numbers.

[Bear Bibeault]

So? What does that have to do with anything? The whole concept of paging ties in with the order with which rows are to be returned. You can specify whatever sorting you like with an ORDER BY clause.

There's a JSP FAQ entry on this subject, by the way.

[Diego Pedrosa]

Hi,

I think you can solve this issue with the 'LIMIT' SQL keyword.
Read this: Paging in SQL

[Andrew Carney]

Hi Diego,

Nice one! I'm going to give it a go!

[Pat Farrell]

Originally posted by Roy Cohen:


Interesting solution, the only problem is that they key is not something numeric that I can run on, it's random numbers.

sounds like a good reason to have an autoincrement field in the table. Key it, and you are ready to go.

If you don't index the column, this approach can get really slow.

[Jan Cumps]

Here's the link to this nice JavaRanch Howto from the JSP FAQ:
PaginationOrPaging : How do I limit the number of rows displayed in the browser?
Regards, Jan
[ November 13, 2007: Message edited by: Jan Cumps ]

[John Simpson]

I'm probably missing something here, but I can't see a solution that will work with un-ordered data.
If the data is not ordered, then can you guarantee that rows will be returned in the same relative position over multiple queries?
Or is the data ordered but not keyed?

John
[ November 13, 2007: Message edited by: John Simpson ]

[Paul Campbell]

Originally posted by John Simpson:
I'm probably missing something here, but I can't see a solution that will work with un-ordered data.
If the data is not ordered, then can you guarantee that rows will be returned in the same relative position over multiple queries?
Or is the data ordered but not keyed?

John

[ November 13, 2007: Message edited by: John Simpson ]

you include an order by clause in your query.