FIRST_VALUE

Syntax

FIRST_VALUE(expr) OVER (
  [ PARTITION BY partition_expression ]
  [ ORDER BY order_list ]
) 

Description

FIRST_VALUE returns the first result from an ordered set, or NULL if no such result exists.

Examples

CREATE TABLE t1 (
  pk int primary key,
  a int,
  b int,
  c char(10),
  d decimal(10, 3),
  e real
);

INSERT INTO t1 VALUES
( 1, 0, 1,    'one',    0.1,  0.001),
( 2, 0, 2,    'two',    0.2,  0.002),
( 3, 0, 3,    'three',  0.3,  0.003),
( 4, 1, 2,    'three',  0.4,  0.004),
( 5, 1, 1,    'two',    0.5,  0.005),
( 6, 1, 1,    'one',    0.6,  0.006),
( 7, 2, NULL, 'n_one',  0.5,  0.007),
( 8, 2, 1,    'n_two',  NULL, 0.008),
( 9, 2, 2,    NULL,     0.7,  0.009),
(10, 2, 0,    'n_four', 0.8,  0.010),
(11, 2, 10,   NULL,     0.9,  NULL);

SELECT pk, FIRST_VALUE(pk) OVER (ORDER BY pk) AS first_asc,
           LAST_VALUE(pk) OVER (ORDER BY pk) AS last_asc,
           FIRST_VALUE(pk) OVER (ORDER BY pk DESC) AS first_desc,
           LAST_VALUE(pk) OVER (ORDER BY pk DESC) AS last_desc
FROM t1
ORDER BY pk DESC;

+----+-----------+----------+------------+-----------+
| pk | first_asc | last_asc | first_desc | last_desc |
+----+-----------+----------+------------+-----------+
| 11 |         1 |       11 |         11 |        11 |
| 10 |         1 |       10 |         11 |        10 |
|  9 |         1 |        9 |         11 |         9 |
|  8 |         1 |        8 |         11 |         8 |
|  7 |         1 |        7 |         11 |         7 |
|  6 |         1 |        6 |         11 |         6 |
|  5 |         1 |        5 |         11 |         5 |
|  4 |         1 |        4 |         11 |         4 |
|  3 |         1 |        3 |         11 |         3 |
|  2 |         1 |        2 |         11 |         2 |
|  1 |         1 |        1 |         11 |         1 |
+----+-----------+----------+------------+-----------+

CREATE OR REPLACE TABLE t1 (i int);
INSERT INTO t1 VALUES (1),(2),(3),(4),(5),(6),(7),(8),(9),(10);

SELECT i,
  FIRST_VALUE(i) OVER (ORDER BY i ROWS BETWEEN CURRENT ROW and 1 FOLLOWING) AS f_1f,
  LAST_VALUE(i) OVER (ORDER BY i ROWS BETWEEN CURRENT ROW and 1 FOLLOWING) AS l_1f,
  FIRST_VALUE(i) OVER (ORDER BY i ROWS BETWEEN 1 PRECEDING AND 1 FOLLOWING) AS f_1p1f,
  LAST_VALUE(i) OVER (ORDER BY i ROWS BETWEEN 1 PRECEDING AND 1 FOLLOWING) AS f_1p1f,
  FIRST_VALUE(i) OVER (ORDER BY i ROWS BETWEEN 2 PRECEDING AND 1 PRECEDING) AS f_2p1p,
  LAST_VALUE(i) OVER (ORDER BY i ROWS BETWEEN 2 PRECEDING AND 1 PRECEDING) AS f_2p1p,
  FIRST_VALUE(i) OVER (ORDER BY i ROWS BETWEEN 1 FOLLOWING AND 2 FOLLOWING) AS f_1f2f,
  LAST_VALUE(i) OVER (ORDER BY i ROWS BETWEEN 1 FOLLOWING AND 2 FOLLOWING) AS f_1f2f
FROM t1;

+------+------+------+--------+--------+--------+--------+--------+--------+
| i    | f_1f | l_1f | f_1p1f | f_1p1f | f_2p1p | f_2p1p | f_1f2f | f_1f2f |
+------+------+------+--------+--------+--------+--------+--------+--------+
|    1 |    1 |    2 |      1 |      2 |   NULL |   NULL |      2 |      3 |
|    2 |    2 |    3 |      1 |      3 |      1 |      1 |      3 |      4 |
|    3 |    3 |    4 |      2 |      4 |      1 |      2 |      4 |      5 |
|    4 |    4 |    5 |      3 |      5 |      2 |      3 |      5 |      6 |
|    5 |    5 |    6 |      4 |      6 |      3 |      4 |      6 |      7 |
|    6 |    6 |    7 |      5 |      7 |      4 |      5 |      7 |      8 |
|    7 |    7 |    8 |      6 |      8 |      5 |      6 |      8 |      9 |
|    8 |    8 |    9 |      7 |      9 |      6 |      7 |      9 |     10 |
|    9 |    9 |   10 |      8 |     10 |      7 |      8 |     10 |     10 |
|   10 |   10 |   10 |      9 |     10 |      8 |      9 |   NULL |   NULL |
+------+------+------+--------+--------+--------+--------+--------+--------+

See Also

• LAST_VALUE