Purpose
This function calculates the cumulative distribution of a value in a set of values. It is similar to the CUME_DIST function. You can use this function as an aggregate or analytic function.
As an aggregate function,
PERCENT_RANKcalculates the position percentage of a value in a set. The return value is in the range (0, 1]. If there areNrows of data, and the value ofexpris greater than the value of the second row and less than the value of the third row, the position percentage is2/N. The number of constant parameter expressions must be the same as the number of expressions in theORDER BYclause of the aggregate function, and their types must be compatible. If a specified value is repeated in the grouping sequence, the two identical values are treated as one value.As an analytic function,
PERCENT_RANKcalculates the percentage ranking of each row in a column or combination of columns. The return value is in the range [0, 1]. When there are duplicate ranking values, the same ranking is assigned to the rows with the same values, and the number of rows with the same value is recorded in the next ranking. ThePERCENT_RANKfunction for the first row in any set is0. The position percentage is calculated as: position percentage = rank / maximum rank. For example, see the following table:N Rank Position Percentage A 0 0 B 1 0.25 C 2 0.5 D 3 0.75 E 4 1
Syntax
/*Aggregate syntax*/
PERCENT_RANK(expr [, expr ...]) WITHIN GROUP
( ORDER BY expr_col [ DESC | ASC ][ NULLS { FIRST | LAST } ]
[,expr_col [ DESC | ASC ][ NULLS { FIRST | LAST } ]]...
)
/*Analytic syntax*/
PERCENT_RANK( ) OVER ([query_partition_clause] order_by_clause)
Parameters
| Parameter | Description |
|---|---|
| expr | Specifies the value to query. |
| expr_col | Specifies the column name corresponding to the value to query. |
| DESC | ASC | Specifies the sorting order. This is an optional parameter.
|
| NULLS { FIRST | LAST } | Specifies the position of NULL values in expr_col after sorting. This is an optional parameter.
|
| OVER | Specifies the window for calculation using the OVER clause. For more information, see Analytic Function Description. |
Return type
NUMBER
Examples
Assume that the emp_msg table has been created.
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
Aggregate function example
Returns the position percentage of 3300 in the sal column.
obclient> SELECT PERCENT_RANK(3300) WITHIN GROUP (ORDER BY sal) FROM emp_msg;
+-------------------------------------------+
| PERCENT_RANK(3300)WITHINGROUP(ORDERBYSAL) |
+-------------------------------------------+
| .8 |
+-------------------------------------------+
1 row in set
Analytic function example
Groups by the deptno column and sorts the sal column in descending order, then returns the position percentage of each value in the sal column.
obclient> SELECT deptno,ename,sal,
PERCENT_RANK() OVER (PARTITION BY deptno ORDER BY sal DESC) AS pr1
FROM emp_msg;
+--------+--------+------+-------------------------------------------+
| DEPTNO | ENAME | SAL | PR1 |
+--------+--------+------+-------------------------------------------+
| 10 | KING | 5300 | 0 |
| 10 | CLARK | 2750 | .5 |
| 10 | MILLER | 1600 | 1 |
| 20 | FORD | 3300 | 0 |
| 20 | SCOTT | 3300 | 0 |
| 20 | JONES | 3275 | .5 |
| 20 | ADAMS | 1400 | .75 |
| 20 | SMITH | 1100 | 1 |
| 30 | BLAKE | 3150 | 0 |
| 30 | ALLEN | 1900 | .1666666666666666666666666666666666666667 |
| 30 | TURNER | 1800 | .3333333333333333333333333333333333333333 |
| 30 | SCLARK | 1750 | .5 |
| 30 | MARTIN | 1550 | .6666666666666666666666666666666666666667 |
| 30 | WARD | 1550 | .6666666666666666666666666666666666666667 |
| 30 | JAMES | 1250 | 1 |
+--------+--------+------+-------------------------------------------+
15 rows in set