如何使用连接查询从两个以上的表中获取数据，而无需外键和主键

Question

Once I need your help,

I have three table in my database.

1> wedding

Column Name    Data Type
-------------------------------------
wedID          Int (primary key)
wedName        varchar (50)

2> selectSite

Column Name   Data Type
-----------------------------------
wedID         Int (without foreign key and primary key with null allow)
siteID        Int (without foreign key and primary key with null allow)
siteStatus    varchar(50)

3> webSite

Column Name   Data Type
--------------------------------      
siteID        Int (Primary Key) 
siteName      varchar(50)
siteFile      varchar(MAX)

I want the following output:

 ws.siteID     ws.siteName     ws.siteFile    s.wedID   s.sitestatus
 ----------------------------------------------------------------------------
 1              Show           show.jpeg      6         Yes
 2              My View        my view.png    5     
 3              Dream          dream.jpeg     3     

ws is alias of webSite table, s is alias of siteSelect table.

All data from webSite table and only data from siteSelect where s.siteStatus do not display Yes if wedID not match

I try following sql query

select 
    DISTINCT(ws.siteID), s.wedID, ws.siteName, 
    ws.siteFile, s.siteStatus 
from wedding wd, webSite ws 
left outer join siteSelect s on ws.siteID = s.siteID 
where wd.wedID = @wedID

but output is like this:

 ws.siteID     ws.siteName     ws.siteFile    s.wedID   s.sitestatus
 -----------------------------------------------------------------------
 1              Show           show.jpeg      6         Yes
 2              My View        my view.png    5         Yes
 3              Dream          dream.jpeg     3         Yes

Answer 1

DEMO SQL FIDDLE

Check the demo add some values as you having and run this query

select 
   ws.siteId, ws.siteName, ws.siteFile, ss.wedID,
   (case 
      when ss.wedID = 1 then ss.siteStatus else '' end) as siteStatus
from 
   website ws 
join 
   selectsite ss on ss.siteID=ws.siteID

let me knw if any prob

Answer 2

try this

select 
    DISTINCT(ws.siteID), s.wedID, ws.siteName, ws.siteFile, 
    (case 
        when s.wedID = @wedID 
        then s.siteStatus 
        else '' end) as siteStatus, wd.wedName
from webSite ws  
left join selectSite s on ws.siteID = s.siteID  
Left Join wedding wd on wd.wedID = s.wedID