Returns the nth expression.
index: An INTEGER expression greater than 0.
exprN: Any expression that shares a least common type with all
The result has the type of the least common type of the
Index must be between 1 and the number of
expr. If index is out of bounds, an INVALID_ARRAY_INDEX error is raised.
If spark.sql.ansi.enabled is
false the function returns
NULL instead of an error if the index is out of bound.