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SingleStoreDB v8.1

NTH_VALUE

Returns an expression evaluated at the nth row of the window frame.

If there are fewer than n rows in the frame, returns NULL. For an overview of window functions in SingleStoreDB, see Window Functions Guide.

Syntax

NTH_VALUE ( expression, n ) OVER (
    [PARTITION BY (col | expr), ...]
    [ORDER BY (col | expr), ...]
    [frame_clause]
)

Arguments

  • expression: any expression. This may be a column name, the result of another function, or a math operation.

  • n: an integer or integer expression.

Return Type

The result type of expression

Examples

CREATE TABLE nth_example (a int, b int);

INSERT INTO nth_example VALUES (1, 2), (2, 2), (3, 3), (4, 3);

SELECT a, NTH_VALUE(a, 2) OVER (ORDER BY a) FROM nth_example;

****
+------+-----------------------------------+
| a    | NTH_VALUE(a, 2) OVER (ORDER BY a) |
+------+-----------------------------------+
|    1 |                              NULL |
|    2 |                                 2 |
|    3 |                                 2 |
|    4 |                                 2 |
+------+-----------------------------------+
SELECT a, NTH_VALUE(a, case when a > 2 then 1 else 2 end) OVER
        (ORDER BY a rows between unbounded preceding and unbounded following) as nth_value FROM nth_example;

****
+------+-----------+
| a    | nth_value |
+------+-----------+
|    1 |         2 |
|    2 |         2 |
|    3 |         1 |
|    4 |         1 |
+------+-----------+
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