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Aggregate & Window Functions
Aggregate & Window Functions
This chapter explains the aggregate and window functions in detail.
Aggregation Functions
Aggregate functions produce a single result from a set of input values. The following table describes the pst of aggregate functions in detail.
| S.No. | Function & Description |
|---|---|
| 1 |
Averages a column of all records in a data source. |
| 2 |
Returns the coefficient of correlation between a set of number pairs. |
| 3 |
Returns the number rows. |
| 4 |
Returns the largest value of the selected column. |
| 5 |
Returns the smallest value of the selected column. |
| 6 |
Returns the sum of the given column. |
| 7 |
Returns the last value of the given column. |
Window Function
The Window functions execute on a set of rows and return a single value for each row from the query. The term window has the meaning of set of row for the function.
The Window function in a query, defines the window using the OVER() clause.
The OVER() clause has the following capabipties −
Defines window partitions to form groups of rows. (PARTITION BY clause)
Orders rows within a partition. (ORDER BY clause)
The following table describes the window functions in detail.
| Function | Return type | Description |
|---|---|---|
| int | Returns rank of the current row with gaps. | |
| int | Returns the current row within its partition, counting from 1. | |
| Same as input type | Returns value evaluated at the row that is offset rows after the current row within the partition. If there is no such row, default value will be returned. | |
| Same as input type | Returns value evaluated at the row that is offset rows before the current row within the partition. | |
| Same as input type | Returns the first value of input rows. | |
| Same as input type | Returns the last value of input rows. |