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Note: results below are from 10.2 348ccb6f038a6c1
create table t1 (i int);
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insert into t1 values (1),(2),(3),(4),(5),(6),(7),(8),(9),(10);
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MariaDB [test]> select i, first_value(i) OVER ( order by i rows between current row and current row ) from t1;
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+------+-----------------------------------------------------------------------------+
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| i | first_value(i) OVER ( order by i rows between current row and current row ) |
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+------+-----------------------------------------------------------------------------+
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| 1 | 1 |
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| 2 | 1 |
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| 3 | 1 |
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| 4 | 1 |
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| 5 | 1 |
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| 6 | 1 |
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| 7 | 1 |
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| 8 | 1 |
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| 9 | 1 |
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| 10 | 1 |
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+------+-----------------------------------------------------------------------------+
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10 rows in set (0.00 sec)
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NTH_VALUE works fine:
MariaDB [test]> select i, nth_value(i,1) OVER ( order by i rows between current row and current row ) from t1;
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+------+-----------------------------------------------------------------------------+
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| i | nth_value(i,1) OVER ( order by i rows between current row and current row ) |
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+------+-----------------------------------------------------------------------------+
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| 1 | 1 |
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| 2 | 2 |
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| 3 | 3 |
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| 4 | 4 |
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| 5 | 5 |
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| 6 | 6 |
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| 7 | 7 |
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| 8 | 8 |
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| 9 | 9 |
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| 10 | 10 |
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+------+-----------------------------------------------------------------------------+
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10 rows in set (0.00 sec)
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PostgreSQL 9.4 returns the same result for both queries:
postgres=# select i, first_value(i) OVER ( order by i rows between current row and current row ) from t1;
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i | first_value
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----+-------------
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1 | 1
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2 | 2
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3 | 3
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4 | 4
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5 | 5
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6 | 6
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7 | 7
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8 | 8
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9 | 9
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10 | 10
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(10 rows)
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postgres=# select i, nth_value(i,1) OVER ( order by i rows between current row and current row ) from t1;
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i | nth_value
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----+-----------
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1 | 1
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2 | 2
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3 | 3
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4 | 4
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5 | 5
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6 | 6
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7 | 7
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8 | 8
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9 | 9
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10 | 10
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(10 rows)
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