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  1. Preface
  2. Function reference
  3. Constants
  4. Operators
  5. Dates
  6. Functions
  7. System variables
  8. Datatype reference

Function Reference

Function Reference

Aggregate functions as window functions

Aggregate functions as window functions

In addition to the LEAD and the LAG functions, you can use aggregate functions as window functions. When you use an aggregate function like SUM or AVG as a window function, you can perform running calculations. Window functions are more flexible than stateful functions because you can set a specific end offset.
To use an aggregate function as a window function, you must define a frame in the window properties to limit the scope of the calculation. The aggregate function performs a calculation across the frame and produces a single value for each row.

Example

You are a lumber salesperson who sold different quantities of wood over the past two years. You want to calculate a running total of sales quantities.
The following table lists each sale ID, the date, and the quantity sold:
Sale_ID
Date
Quantity
30001
2016-08-02
10
10001
2016-12-24
10
10005
2016-12-24
30
40001
2017-01-09
40
10006
2017-01-18
10
20001
2017-02-12
20
A SUM function adds all the values and returns one output value. To get a running total for each row, you can define a frame for the function boundaries.
You configure the following properties on the
Window
tab:
  • Start offset: All Rows Preceding
  • End offset: 0
  • Order Key: Date Ascending
You define the following aggregate function:
SUM (Quantity)
SUM adds the quantity in the current row to the quantities in all the rows preceding the current row. The function returns a running total for each row.
The following table lists a running sum for each date:
Sale_ID
Date
Quantity
Total
30001
2016-08-02
10
10
10001
2016-12-24
10
20
10005
2016-12-24
30
50
40001
2017-01-09
40
90
10006
2017-01-18
10
100
20001
2017-02-12
20
120

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