lookahead aggregate
An expression requiring two passes through the data rows in a data source to calculate a value. For example, to calculate the percentage of a total sales amount that each product category represents requires one pass to calculate the total sales amount for all product categories. A second pass calculates the total sales amount for each product category then compares that value to the total for all categories to compute a percentage value.
Related terms
data row, data source, expression, value
Contrast with
running aggregate

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