2010-08-16 166 views
0

有人請解釋我如何做到這一點的查詢工作SQL Server存儲過程

SELECT 'WRITEBOARDCOMMENT' AS Type, 
wbc.CommentText AS Content, 
wb.WBId AS Id, 
null AS ToDoListName, 
null AS DueDate, 
u.FirstName + ' ' + u.LastName AS ActivityBy, 
wbc.[Date] as Date, 
u.FirstName + ' ' + u.LastName as PartyName, 
comp.CompanyId AS CompanyId, 
comp.CompanyName AS CompanyName, 
p.ProjectName, 
p.ProjectId, 
wbc.WBCmtId AS SubId, 
p.ProjectStartPageId AS ProjectStartPageId 
FROM 
WriteboardComment AS wbc, 
WriteBoardVersions AS wbv, 
WriteBoard AS wb, 
Project AS p,[user] AS u, 
Company AS comp 
where 
wbc.wbversionid=wbv.wbversionsid and 
wbv.WBId=wb.WBId and 
wb.ProjectId=p.ProjectId and 
[email protected] and 
wbc.CommentedBy=u.UserId and 
p.PrimaryCompanyId=comp.CompanyId 

什麼是連接表像this.I的優勢,發現了這一個在一個項目DB代碼。

回答

0

這曾經是做聯合的舊風格。經典連接版本沒有優勢。

1

沒有優勢,這是一個古老的風格加入,你可以輕鬆地拍攝自己的腳,當你陷入困境/離開了WHERE子句,然後創建一個cartesian product/cross join錯誤