SQL Server性能查询

Question

I have some troubles with this query (view).

I'm using SQL Server 2012. With few Record the query is fast but after that I add only 1000 records (Links) it becomes very slow (over 23 seconds)

I have to take a random Link for every host in database,so I used Row_Number and partition by.

Links table has 1000 records and host table has 10 record but the query is so slow

Any advice for increase performance?

UPDATE I need to get foreach Host a Random Link (could be 1 or 2 or 3 depends on Host.numLinksPerWork)

;WITH MyCte As
( 
SELECT DISTINCT link.namUrl, host.uidHost, host.namHost AS Hostname,
[user].uidUser, usrProfile.UserName AS Username, host.numLinksPerWork, 
referer.namUrl AS refererLink,host.Min, host.Max,ROW_NUMBER() 
OVER (PARTITION BY host.numLinksPerWork, host.uidHost ORDER BY newid()) AS Number
FROM  Links link JOIN
Users[user] ON [user].uidUser = link.codUser JOIN
Profile usrProfile ON usrProfile.UserId = [user].uidUser JOIN
Hosts host ON host.uidHost = link.codHost JOIN
Referers referer ON referer.codHost = host.uidHost JOIN
Referers referer2 ON referer.codUser = [user].uidUser
WHERE [user].flgBanned = 0
)

SELECT MyCte.uidHost, MyCte.uidUser, MyCte.namUrl, MyCte.refererLink, 
MyCte.Hostname, MyCte.Username, MyCte.Min, MyCte.Max FROM MyCte
WHERE MyCte.Number <= MyCte.numLinksPerWork!

Similar Diagram

Answer 1

I Fixed the problem... The double join on the same table which is wrong OFC ,It slowed down the query!

Referers referer ON referer.codHost = host.uidHost JOIN
Referers referer2 ON referer.codUser = [user].uidUser

removing useless Join(s) it's fast!