I have a SQL Server 2008 R2 database. This database has two tables called Pictures and PictureUse.
Picture table has the following columns:
Id (int)
PictureName (nvarchar(max))
CreateDate (datetime )
PictureUse table has the following columns :
Id (int)
Pictureid (int)
CreateDate (datetime )
I need to create a computed column in the Picture table which tells me that how many times this picture has been clicked.any help ?
You can create a user-defined function for that:
CREATE FUNCTION dbo.CountUses(@pictureId INT)
RETURNS INT
AS
BEGIN
RETURN
(SELECT Count(id)
FROM PictureUse
WHERE PictureId = @PictureId)
END
The computed column can then be added like this:
ALTER TABLE dbo.Picture
ADD NofUses AS dbo.CountUses(Id)
However, I would rather make a view for this:
CREATE VIEW PictureView
AS
SELECT Picture.Id,
PictureName,
Picture.CreateDate,
Count(PictureUse.Id) NofUses
FROM Picture
JOIN PictureUse
ON Picture.Id = PictureUse.PictureId
GROUP BY Picture.Id,
PictureName,
Picture.CreateDate
function and Computed column
CREATE FUNCTION dbo.CountUses(INT @pictureId) should be CREATE FUNCTION dbo.CountUses(@pictureId INT). Also the function is missing BEGIN .. END and a RETURN
A computed column may only reference other columns in the same table. You could (as per jeroenh's answer) use a UDF, but the column won't be stored or be indexable and so it has to be recomputed every time the row is accessed.
You could create an indexed view that contains this information (if, as I suspect, it's just the count of rows from PictureUse):
CREATE VIEW dbo.PictureStats
WITH SCHEMABINDING
AS
SELECT PictureID,COUNT_BIG(*) as Cnt from dbo.PictureUse
GO
CREATE UNIQUE CLUSTERED INDEX IC_PictureStats on dbo.PictureStats (PictureID)
Behind the scenes, SQL Server will effectively create a table that contains the results of this view, and every insert, update or delete to PictureUse will maintain this results table automatically for you.
you dont have to add the computed column to your table, because, after its updated,if the original table data got changed, then data become inconsistent , you can always use this select statement to get the column count, or create it as a view
select p.id,count(*) as count
from Picture P
join PictureUse U
on p.id=u.Pictureid
group by p.id
This will work
SELECT P.id
,P.PictureName
,COUNT(P.id) as [Count]
FROM Picture P
INNER JOIN PictureUse PU
ON P.id=PU.Pictureid
GROUP BY P.id,P.PictureName
try this
select count(distict pictureid) from pictureuse
inner join picture on picture.id=pictureuse.pictureid
