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FIRST_VALUE
Value function. Returns an expression evaluated at the first row of the window frame. If there are no rows in the frame, returns NULL.
For an overview of window functions in MemSQL, see Window Functions Guide.
Syntax
FIRST_VALUE ( expression ) 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.
Return Type
The result type of expression
Examples
memsql> create table example (a int, b int);
memsql> insert into example values (1, 2), (2, 2), (3, 3), (4, 3);
memsql> select a, first_value(a) over(order by (a)) from example;
+------+-----------------------------------+
| a | first_value(a) over(order by (a)) |
+------+-----------------------------------+
| 1 | 1 |
| 2 | 1 |
| 3 | 1 |
| 4 | 1 |
+------+-----------------------------------+
memsql> select a, first_value(a) over(order by (a) rows between current row and unbounded following) from example;
+------+------------------------------------------------------------------------------------+
| a | first_value(a) over(order by (a) rows between current row and unbounded following) |
+------+------------------------------------------------------------------------------------+
| 1 | 1 |
| 2 | 2 |
| 3 | 3 |
| 4 | 4 |
+------+------------------------------------------------------------------------------------+
