The following table provides the semantics of the allowable combinations of window functions, Teradata-specific functions, aggregate functions, and the GROUP BY clause.
| Combination | Semantics | ||||
|---|---|---|---|---|---|
| Window Function | Teradata-Specific Function | Aggregate Function | GROUP BY Clause | ||
| X | A value is computed for each row. | ||||
| X | A value is computed for each row. The entire table constitutes a single group, or partition, over which the Teradata-specific function runs. | ||||
| X | One aggregate value is computed for the entire table. | ||||
| X | X | GROUP BY collapses all rows with the same value for the group-by columns into a single row, and a value is computed for each resulting row. | |||
| X | X | GROUP BY determines the partitions over which the Teradata-specific function runs. The clause does not collapse all rows with the same value for the group-by columns into a single row. | |||
| X | X | An aggregation is performed for each group. | |||
| X | X | Teradata-specific functions do not have partitions. The whole table is one partition. | |||
| X | X | X | GROUP BY determines partitions for Teradata-specific functions. GROUP BY does not collapse all rows with the same value for the group-by columns into a single row, and does not affect window function computation. | ||
| X | X | X | GROUP BY collapses all rows with the same value for the group-by columns into a single row. For window functions, a value is computed for each resulting row; for aggregate functions, an aggregation is performed for each group. | ||