NTH_VALUE Window Function
The NTH_VALUE window function returns the expression value of the specified row of the window frame relative to the first row of the window.
Syntax
NTH_VALUE (expr, offset) [ IGNORE NULLS | RESPECT NULLS ] OVER ( [ PARTITION BY window_partition ] [ ORDER BY window_ordering frame_clause ] )
Arguments
- expr
-
The target column or expression that the function operates on.
- offset
-
Determines the row number relative to the first row in the window for which to return the expression. The offset can be a constant or an expression and must be a positive integer that is greater than 0.
- IGNORE NULLS
-
An optional specification that indicates that Amazon Redshift should skip null values in the determination of which row to use. Null values are included if IGNORE NULLS is not listed.
- RESPECT NULLS
-
Indicates that Amazon Redshift should include null values in the determination of which row to use. RESPECT NULLS is supported by default if you do not specify IGNORE NULLS.
- OVER
-
Specifies the window partitioning, ordering, and window frame.
- PARTITION BY window_partition
-
Sets the range of records for each group in the OVER clause.
- ORDER BY window_ordering
-
Sorts the rows within each partition. If ORDER BY is omitted, the default frame consists of all rows in the partition.
- frame_clause
-
If an ORDER BY clause is used for an aggregate function, an explicit frame clause is required. The frame clause refines the set of rows in a function's window, including or excluding sets of rows in the ordered result. The frame clause consists of the ROWS keyword and associated specifiers. See Window Function Syntax Summary.
The NTH_VALUE window function supports expressions that use any of the Amazon Redshift data types. The return type is the same as the type of the expr.
Examples
See NTH_VALUE Window Function Examples.