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Greenplum - Architecture and SQL by Leona Coffing, Tom Coffing

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Chapter 16 – OLAP Functions

“Don’t count the days, make the days count.”

- Mohammad Ali

CSUM

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This ANSI version of CSUM is SUM () Over. Right now, the syntax wants to see the sum of the Daily_Sales after it is first sorted by Sale_Date. Rows Unbounded Preceding means to start calculating from the first row, and continue calculating until the last row. This Rows Unbounded Preceding makes this a CSUM. The ANSI Syntax seems difficult, but only at first.

CSUM – The Sort Explained

SELECT   Product_ID , Sale_Date, Daily_Sales,

SUM(Daily_Sales) OVER (ORDER BY  Sale_Date

ROWS UNBOUNDED PRECEDING) AS CsumAnsi

FROM  Sales_Table

WHERE Product_ID BETWEEN ...

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