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How do I page rsults in SQL Express with a JOIN in the WHERE clause

Posted on 2008-10-09
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Last Modified: 2012-05-05
I have a stored procedure below that returns a bunch of results.  This stored procedure works exactly as I want it to.  Except now I want to do paging within the stored procedure.

I have looked at various samples throughout the Net but don't quite get it.  None of the examples I have seen have any form of SELECT statement with anything outside the ordinary.  They also all seem to order by the IDENTITY column of the selected table or some OVER statement that allows the ORDER BY clause to use a column in the selected table.  I want to order by a COUNT through a joined table.

It is entirely possible the count may be "0" for many of these items as well (no restaurants added as favourites yet and in the future obviously not all restaurants will be added as favourites).  A variation excluding the 0 counted restaurants would be nice but most importantly I need a pageable version with or without the 0 counted restaurants.

I have basically no knowledge of paging so treat me as a complete novice in this.  Also consider the passed variables as PageSize and PageNumber (1 based not 0 based) not StartRow and EndRow as I have seen in some examples.
SELECT Restaurant.* FROM Restaurant
	LEFT JOIN (SELECT RestaurantId, COUNT(*) AS RecCount FROM UserFavourites GROUP BY RestaurantID ) As C 
		ON Restaurant.RestaurantId=C.RestaurantId
	WHERE Restaurant.Active = 1 
	ORDER BY C.RecCount DESC

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Question by:dij8
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8 Comments
 
LVL 7

Expert Comment

by:Zippit
ID: 22683640
In MySQL it's pretty straightforward.  You can use the Limit X,Y statement to do so where X is the record number to start returning and Y is the number of records to return.  So the following would return 10 records starting at the 25th record:

SELECT *
FROM tbl_myTable
LIMIT 25, 10

Unfortunately MS SQL doesn't have anything quite so easy.  With MS SQL you are going to have to use some kind of "key" field (typically you want it to be a unique column) and the "top" command.  For example...take the following:

SELECT TOP 10 int_myKey, str_name, dtm_dob
FROM tbl_users
WHERE int_myKey > 100
ORDER BY int_myKey ASC

This query will return the 10 records, starting at key 101.  Obviously there are catches here, like if you don't want to sort on the key (if you are confident the names are unique, you can sort on Name and use it in your Where clause).

But that's it.  Other then writing your own paging logic in a storedproc or in the app making use of the data (if your data is in a dataset or a recordset or even XML you could do this fairly easily, but this requires you keep all data in memory in the app.  Not an ideal design).

HTH
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LVL 75

Expert Comment

by:Anthony Perkins
ID: 22683646
The way we do this is by inserting the results into a temporary table that has an identity column and then return the group of rows requested based on the page size and start index.
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LVL 39

Expert Comment

by:BrandonGalderisi
ID: 22683682
I'm working up some sample data to show you how it works, but this should do it.
create procedure up_Restaurant_Get @PageNumber int, @PageSize int
as
set nocount on
;with Restaurants as (
SELECT Restaurant.*, row_number() over(order by by RecCount desc) rn
FROM Restaurant
LEFT JOIN (SELECT RestaurantId, COUNT(*) AS RecCount FROM UserFavourites GROUP BY RestaurantID ) As C 
                ON Restaurant.RestaurantId=C.RestaurantId
        WHERE Restaurant.Active = 1 
)
select * from Restaurants
where (rn-1)/@PageSize = @PageNum

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LVL 39

Accepted Solution

by:
BrandonGalderisi earned 500 total points
ID: 22683761
I was a little off... this one is right though.
set nocount on
go
create table #Restaurant
 (RestaurantID      int
 ,RestaurantName    varchar(20)
 ,Active            bit
 )
go
create table #UserFavorites 
 (restaurantID      int
 ,userid            int
 )
 
go
insert into #Restaurant values(1,'McDonalds',1)
insert into #Restaurant values(2,'Burger King',1)
insert into #Restaurant values(3,'Wendy''s',1)
insert into #Restaurant values(4,'Hardees',1)
insert into #Restaurant values(5,'Arby''s',1)
insert into #Restaurant values(6,'Dairy Queen',2)
insert into #Restaurant values(7,'Red Lobster',1)
insert into #Restaurant values(8,'Olive Garden',1)
insert into #Restaurant values(8,'Pizza Hut',1)
insert into #Restaurant values(8,'Dominos',1)
go
insert into #userFavorites values(1,1)
insert into #userFavorites values(1,2)
insert into #userFavorites values(1,3)
insert into #userFavorites values(1,4)
 
insert into #userFavorites values(2,1)
insert into #userFavorites values(2,2)
insert into #userFavorites values(2,4)
insert into #userFavorites values(2,1)
 
insert into #userFavorites values(3,1)
insert into #userFavorites values(3,4)
 
insert into #userFavorites values(4,7)
insert into #userFavorites values(4,5)
insert into #userFavorites values(4,2)
insert into #userFavorites values(4,1)
insert into #userFavorites values(4,3)
 
insert into #userFavorites values(5,1)
insert into #userFavorites values(5,2)
insert into #userFavorites values(5,3)
insert into #userFavorites values(5,4)
 
insert into #userFavorites values(6,1)
 
insert into #userFavorites values(7,1)
 
 
go
drop procedure up_Restaurant_Get 
go
create procedure up_Restaurant_Get @PageNumber int, @PageSize int
as
set nocount on
;with Restaurants as (
SELECT r.*,isnull(c.reccount,0) as reccount, row_number() over(order  by RecCount desc) rn
FROM #Restaurant r
LEFT JOIN (SELECT RestaurantId, COUNT(*) AS RecCount FROM #UserFavorites GROUP BY RestaurantID ) As C 
                ON r.RestaurantId=C.RestaurantId
        WHERE r.Active = 1 
)
select ((rn-1)/@PageSize)+1,* from Restaurants
where ((rn-1)/@PageSize)+1 = @PageNumber
 
go
exec up_Restaurant_Get 1,8
exec up_Restaurant_Get 1,2
exec up_Restaurant_Get 2,2
exec up_Restaurant_Get 3,3
 
go
drop table #Restaurant
drop table #UserFavorites 

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LVL 10

Author Comment

by:dij8
ID: 22684204
Fantastic result. :-)

Including the creation and inserting of tables well and truly shows how this all works.  A top notch answer above and beyond.

Once I realised I had to remove the # from the two tables that already exist for me and return the UserFavourites to non-American spelling it worked a treat.
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LVL 10

Author Comment

by:dij8
ID: 22684214
Another quick question, is it possible to select all the columns that match the columns in the Restaurant table and NOT select the "reccount" and "rn" columns without listing each column name.

e.g.
select *, NOT reccount, NOT rn from Restaurants
where ((rn-1)/@PageSize)+1 = @PageNumber

I'm expecting this to not be possible so an answer of "no" is, while sad, sufficient.  After all, there's no bonus points.
0
 
LVL 10

Author Comment

by:dij8
ID: 22684233
Forget it, I already worked it out.  Let me know if it is going to cause any issues though.
ALTER PROCEDURE [dbo].[GetMostPopularRestaurants]
	@PageNumber int,
	@PageSize int
AS
SET NOCOUNT ON
;WITH Restaurants AS (
	SELECT r.*,isnull(c.reccount,0) AS reccount, row_number() OVER(ORDER  BY RecCount DESC) rn
	FROM Restaurant r
	LEFT JOIN (SELECT RestaurantId, COUNT(*) AS RecCount FROM UserFavourites GROUP BY RestaurantID ) AS C 
		ON r.RestaurantId=C.RestaurantId
	WHERE r.Active = 1 
)
SELECT Restaurant.* FROM Restaurant
	INNER JOIN Restaurants r ON r.RestaurantId = Restaurant.RestaurantId
WHERE ((r.rn-1)/@PageSize)+1 = @PageNumber

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LVL 39

Expert Comment

by:BrandonGalderisi
ID: 22684581
There is no "select all but columna" syntax in SQL server.  

But as you have found, you don't have to select from both the table and the CTE, just the table.
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