How to have multiple tables with multiple joins
I have three tables that I need to join together and get a combination of results. I have tried using left/right joins but they don't give the desired results.
For example:
Table 1 - STAFF
id name
1 John
2 Fred
Table 2 - STAF开发者_如何学GoFMOBILERIGHTS
id staffid mobilerightsid rights
--this table is empty--
Table 3 - MOBILERIGHTS
id rightname
1 Login
2 View
and what I need is this as the result...
id name id staffid mobilerightsid rights id rightname
1 John null null null null 1 login
1 John null null null null 2 View
2 Fred null null null null 1 login
2 Fred null null null null 2 View
I have tried the following :
SELECT *
FROM STAFFMOBILERIGHTS SMR
RIGHT JOIN STAFF STA
ON STA.STAFFID = SMR.STAFFID
RIGHT JOIN MOBILERIGHTS MRI
ON MRI.ID = SMR.MOBILERIGHTSID
But this only returns two rows as follows:
id name id staffid mobilerightsid rights id rightname
null null null null null null 1 login
null null null null null null 2 View
Can what I am trying to achieve be done and if so how?
Thanks
From your comment its now clear you want a cross join (include all rows from staff and mobilerights). Something like this should do it
SELECT
*
FROM Staff, MobileRights
LEFT OUTER JOIN StaffMobileRights ON StaffMobileRights.StaffId = Staff.Id
The FROM clause specifies that we will be including all rows from the Staff table, and all rows from the MobileRights table. The end result will therefore contain (staff * MobileRights) rows.
To bring in rows from StaffMobileRights then we need a join to that table also. We use a LEFT OUTER join to ensure that we always include the left side (rows in the staff table) but we arent too bothered if no rows exist on the right side (StaffMobileRights table). If no row exists for the join then null values are returned.
What you are probably asking is to see null where is no rights. In the rectangular style that results are always returned, this is the only way to represent it with a simple join:
From PaulG's query i changed it a bit to always get everything form the STAFF table.
SELECT
*
FROM STAFF
RIGHT OUTER JOIN StaffMobileRights ON StaffMobileRights.StaffId = Staff.Id
INNER JOIN MobileRights ON MobileRights.Id = StaffMobileRights.MobileRightsId
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