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Oracle : Analytical function question

  • 12-09-2005 12:18pm
    #1
    bonkey
    Registered Users, Registered Users 2 Posts: 15,443 ✭✭✭✭


    Hi guys...

    Here's an outline of a problem I'm trying to efficiently resolve at the mo:

    TableX contains a large number of rows, which equate to transactions from customers. What I want to find & retrieve is the transactions in a given month for the N customers with the highest transaction totals for that month.

    What I'm thinking at present is that I can use analytical functions in two steps. First, I need to get a total per month/customer against each record:

    [php]

    SELECT dateField
    , CustomerId
    , transactionValue
    , SUM(transactionValue) OVER (PARTITION BY dateField,
    CustomerId) AS MonthlyCustomerTransactionTotal
    FROM <source tables and join information to go here>
    [/php]
    OK...so then, I can wrap this to densely rank the totals:

    [php]
    SELECT dateField
    , CustomerId
    , transactionValue
    , MonthlyCustomerTransactionTotal
    , DENSE_RANK() OVER (PARTITION BY dateField,
    CustomerId
    ORDER BY dateField,
    CustomerId,
    MonthlyCustomerTransactionTotal) as MonthlyCustomerRank
    FROM (
    <SQL from above goes here as a nested-select pseudo-table>
    )
    [/php]
    I can now use this code as the basis for a View, which can be queried for any given month....and the user can specify how many ranked positions he wants.

    What I'm wondering is whether or not I can ditch using nested queries. Can anyone think of / see / tell me of a way to do this?


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