CODEWITHSUNDEEP
sqloracle-databasejoinsubquery
managedheap84
managedheap84

Reputation: 851

Are these SQL statements functionally equivalent?

I'm doing some SQL optimizations but my SQL fu could use some improvement...

Why do a join on a subquery, could this just be a straight inner join, or am I missing something?

        -- Why do a join and a subquery?
        -- INNER JOIN  (
        --          SELECT client_id, session_id, id, customer_id, validity, machine_id, 
        --                  utc_date_completed, itemStatus, totalValue, utc_date_updated, 
        --                  itemValue, itemId, itemName, customField1, customField2, itemPage, itemCurrency
        --          FROM data.dashboard WITH(NOLOCK)
        --          WHERE client_id = @client_id
        --          ) d  ON cm.client_id = d.client_id

        INNER JOIN data.dashboard AS d ON cm.client_id = d.client_id AND d.client_id = @client_id

Upvotes: 0

Views: 54

Answers (1)

xlecoustillier
xlecoustillier

Reputation: 16361

Yes, functionnally they are the same, and you should have better performance doing an INNER JOIN. Check on the execution plan for performance.

And it is far more readable and maintainable.

Upvotes: 1

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