quote:

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Originally posted by webcomber

Hi -

I have a general question about the order of joins. I have noticed that in some of the queries I am looking at, there are lots of LEFT and RIGHT Joins one after the other. My question is which table is considered the LEFT or RIGHT or original table if there are 9 or so joins after it?



For example, if a query says
select ORD.orderID, ORD.CustomerID, EMP.employeeID, SOX.AugitID
FROM Dbo.employees EMP
INNER JOIN
dbo.orders ORD
On
emp.employeeid=ORD.employeeid
LEFT OUTER JOIN
dbo.Customers CUST
ON CUST.CustomerID=ORD.CustomerID
RIGHT OUTER JOIN
SOX.Audit.ID
ON ORD.OrderID = SOX.Audit.ID

the query INNER JOINS Employee and Orders table, but for the LEFT and RIGHT joins, is the Original FROM dbo.Employees EMP always considered the original table from which a LEFT JOIN is done, and if so is the RIGHT OUTER JOIN, the SOX table, taking the JOIN on the original FROM Table FROM Dbo.employees EMP, or from the table preceding the RIGHT OUTER JOIN, the Customers table. This is a simple example, but these queries have one table after another for about 9 - 15 joins (RIGHT, LEFT, etc.). Whatever applies to the simple query above, I will take to the more complex ones.

Thanks -

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quote:

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Originally posted by webcomber

Hello -

I thought the JOIN statement always determined which was the LEFT or RIGHT table. SO I guess in this case, the LEFT table is the result of the first query, and the RIGHT table, Audit, is JOINED to the LEFT JOIN results. I suppose in these cases, we have to track the results of the query for each join.
I am not sure if the ON statement determines any order ??

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quote:

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Originally posted by webcomber

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