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Mystery query
Posted by: DK Johnston
Date: November 06, 2013 12:19AM

Why does the first query take so much longer to execute?

-- Main query: > 100 seconds.
SELECT
customers.CompanyName, customers.City, customers.Country
FROM
customers
WHERE
customers.CustomerID IN (SELECT
orders.customerid
FROM
orders
WHERE
orders.OrderID IN (SELECT
order_details.OrderID
FROM
order_details
WHERE
ProductID = 34));

-- Sub-query: < 2 seconds.
SELECT
orders.customerid
FROM
orders
WHERE
orders.OrderID IN (SELECT
order_details.OrderID
FROM
order_details
WHERE
ProductID = 34);

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Subject
Written By
Posted
Mystery query
November 06, 2013 12:19AM
November 07, 2013 06:58AM
November 07, 2013 07:22PM


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