Purpose
This function returns the value of the measure_expr field in the nth row of the window defined by the analytic_clause.
Syntax
NTH_VALUE (measure_expr, n)
[ FROM { FIRST | LAST } ][ { RESPECT | IGNORE } NULLS ]
OVER (analytic_clause)
Parameters
Parameter |
Description |
|---|---|
| measure_expr | The field to return data from. |
| n | The nth row to return the measurement value from. n is a positive integer. Notice
|
| FROM { FIRST | LAST } | The calculation direction. Optional. Default value is FROM FIRST.
|
| {RESPECT | IGNORE} NULLS | Whether to ignore NULL values. Optional. Default value is RESPECT NULLS.
|
| OVER | Use the OVER clause to define the window for calculation. For more information, see Analytic Functions. |
Return type
The return type is the same as the data type of the measure_expr parameter.
Examples
Assume that the emp_msg table has been created. Query the emp_msg table, group by the deptno column, sort by the sal column in descending order, and return the value of the sal column in the 4th row.
obclient> SELECT * FROM emp_msg;
+--------+--------+------+------+
| DEPTNO | ENAME | SAL | MGR |
+--------+--------+------+------+
| 10 | CLARK | 2750 | 7839 |
| 10 | KING | 5300 | NULL |
| 10 | MILLER | 1600 | 7782 |
| 20 | ADAMS | 1400 | 7788 |
| 20 | FORD | 3300 | 7566 |
| 20 | JONES | 3275 | 7839 |
| 20 | SCOTT | 3300 | 7566 |
| 20 | SMITH | 1100 | 7902 |
| 30 | ALLEN | 1900 | 7698 |
| 30 | BLAKE | 3150 | 7839 |
| 30 | JAMES | 1250 | 7698 |
| 30 | MARTIN | 1550 | 7698 |
| 30 | TURNER | 1800 | 7698 |
| 30 | WARD | 1550 | 7698 |
| 30 | SCLARK | 1750 | 7839 |
+--------+--------+------+------+
15 rows in set
obclient> SELECT deptno,ename,sal,
NTH_VALUE(sal,4) OVER (PARTITION BY deptno ORDER BY sal DESC
ROWS BETWEEN UNBOUNDED PRECEDING AND UNBOUNDED FOLLOWING) AS third_most_sal
FROM emp_msg
ORDER BY deptno,sal DESC;
+--------+--------+------+----------------+
| DEPTNO | ENAME | SAL | THIRD_MOST_SAL |
+--------+--------+------+----------------+
| 10 | KING | 5300 | NULL |
| 10 | CLARK | 2750 | NULL |
| 10 | MILLER | 1600 | NULL |
| 20 | FORD | 3300 | 1400 |
| 20 | SCOTT | 3300 | 1400 |
| 20 | JONES | 3275 | 1400 |
| 20 | ADAMS | 1400 | 1400 |
| 20 | SMITH | 1100 | 1400 |
| 30 | BLAKE | 3150 | 1750 |
| 30 | ALLEN | 1900 | 1750 |
| 30 | TURNER | 1800 | 1750 |
| 30 | SCLARK | 1750 | 1750 |
| 30 | MARTIN | 1550 | 1750 |
| 30 | WARD | 1550 | 1750 |
| 30 | JAMES | 1250 | 1750 |
+--------+--------+------+----------------+
15 rows in set