General information
Forum:
Microsoft SQL Server
Title:
Can you 'force' a join order?
To all,
In Visual FoxPro, you can "force" the order in which a set of tables are joined. For example, with a hierarchicaly structured set of tables (say the classic Customers, Order, Line Items) you can force the order in which the tables are joined:
SELECT * ;
FROM Line_Items ;
WHERE li_OrderNum IN ;
(SELECT O.or_OrderNum ;
FROM FORCE Customers C ;
INNER JOIN Order O ;
ON O.or_CustNum = C.cs_CustNum ;
WHERE C.cs_CustName = 'FRED')
In this example, the join order of the sub select starts with Customers
(which is filtered) and goes to the Order table.
With larger queries, I've seen a 25% improvement in performance using the VFP "FORCE" clause.
Does T-SQL have an analog to VFP's 'FORCE' clause?
Regards,
Thom C.
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