By the end of this chapter you will be able to:

You will also learn how to limit a pipe to read a maximum number of data records.

In this exercise you will select the latest (most recent) sales record for each customer, from the set of combined updates you created in the previous exercise.

Create an aggregate stream

1. In the model toolbar, find 
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     and drag it into the model.
2. Set the stream Name to Latest Package Update.
3. Add a pipe from Combined Updates:
   1. Hover your mouse pointer over the stream Combined Updates.
   2. In the context toolbar, click 
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      .
   3. Click the stream Latest Package Update to connect the pipe.
4. Drag all attributes from Combined Updates to Latest Package Update.
   1. Hover your mouse pointer over the stream Combined Updates again.
   2. In the context toolbar, click 
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      . Phixflow lists the data attributes (column titles) for this stream.
   3. Select all the attributes and drag them into the Latest Package Update settings → Aggregate Attributes section.
      
   4. Click  OK to save and close the Latest Package Updates settings.
   5. Close the attributes pop-up window.
5. In the Channel Package model toolbar, click  Save.

When you next run this model, the Latest Package Updates stream will pull in all the data from the Combined Updates stream.

Group and order data on an input pipe

At the moment the data will come into the aggregate stream in any order. You are going to sort the data as it comes through the input pipe to the aggregate stream.

• Group the data, so that all the records with the same Customer Ref number are adjacent in the table.
• Sort the data by date, newest to oldest, using Sales Date. This means that the first record delivered by the input pipe, for each Customer Ref, is the most recent for that customer.

1. Double click on the pipe from the  Combined Updates stream.
2. Expand the Sort/Group section toolbar.
3. In the section toolbar, click
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    (check  - Show Stream Attributes)?? Phixflow opens a list of the attributes - how does it know these?
   
4. Drag in CustomerRef. By default, it is set to have Group ticked and Direction A-Z
5. Drag in SalesDate. To make this an ordering attribute:
   1. Double-click on SalesDate in the Sort/Group grid
   2. Set the Sort Direction to descending: Z-A
      
   3. Untick the Group flag.
   4. Click  OK to save the change and close the attribute settings.
6. Set Maximum Number of Records per Group to 1.
7. Click  OK to save and close the pipe settings.
   

This setting means that for each key value – in this case for each value of CustomerRef – only the first record will be returned; since you have also ordered by SalesDate descending, this will be the latest (most recent) record for each CustomerRef

This is effectively filtering out old records for the same customer.

Test your new Stream

• Run analysis on your new stream
• Make sure that for all customers the most recent sales update has been selected