[GitHub] [spark] HyukjinKwon commented on a change in pull request #28685: [SPARK-27951][SQL] Support ANSI SQL NTH_VALUE window function

[GitBox <gi...@apache.org>]

HyukjinKwon commented on a change in pull request #28685:
URL: https://github.com/apache/spark/pull/28685#discussion_r437941258



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File path: sql/core/src/main/scala/org/apache/spark/sql/functions.scala
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@@ -993,6 +993,30 @@ object functions {
     Lead(e.expr, Literal(offset), Literal(defaultValue))
   }
 
+  /**
+   * Window function: returns the value that is the `offset`th row of the window frame
+   * (counting from 1), and `null` if the size of window frame is less than `offset` rows.
+   *
+   * This is equivalent to the nth_value function in SQL.
+   *
+   * @group window_funcs
+   * @since 3.0.0
+   */
+  def nth_value(columnName: String, offset: Int): Column = {

Review comment:
       @beliefer, how is it different from `leg`?




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