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Optimization - FROM Clause

Optimization - FROM Clause

Since this clause executes first, it is our first opportunity to narrow down possible record set sizes. This is why I put as many of my ON rules (for joins) as possible in this area as opposed to in the WHERE clause:
FROM
    contact c
INNER JOIN
    display_status d
ON
    (
            c.display_status_id = d.id
        AND
            d.is_active = 1
        AND
            d.is_viewable = 1 
    )
This way, by the time we get to the WHERE clause, we will have already excluded rows where is_active and is_viewable do not equal 1.
Read more: SQL Query Order of Operations
FROM-clause optimization

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