Wave Analytics SAQL Reference

SAQL Overview
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SAQL Basic Elements
SAQL Operators
SAQL Statements
SAQL Functions
Aggregate Functions
Date Functions
String Functions
Math Functions
Windowing Functions
coalesce()
Query Performance
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coalesce()

Use the coalesce() function to get the first non-null value from a list of parameters.
1coalesce(value1 , value2 , value3 , ... )
For example, the following statements ensure that a non-null grouping value is used when doing a full outer join.
1accounts = load "em/cogroup/accounts";
2opps = load "em/cogroup/opportunities";
3c = cogroup accounts by 'Year' full, opps by 'Year';
4c = foreach c generate coalesce(accounts::'Year',opps::'Year') as 'Group';
You can also use the coalesce() function to replace nulls with a default value. For example, the following statements set the default for division by zero to a non-null value.
1q = load "dataset";
2q = group q by 'Year';
3q = foreach q generate 'Year', coalesce(sum(Amount)/sum(Quantity),0) as 'AvgPrice';