Purpose
RANK() returns the rank of a value in a group of values. Rows with equal values for the ranking criteria receive the same rank and are considered tied rows. OceanBase Database adds the number of tied rows to the tied rank to calculate the next rank. You can use it as an aggregate or analytic function.
Note
- As an aggregate function, the
RANK()function calculates the rank of a row based on the assumed row identified by theexprparameter in relation to the specified rank specification. Theexprexpression matches to the expression in theORDER BYaggregate clause by position. Therefore, the number of arguments must be the same and their types must be compatible. - As an analytic function,
RANK()calculates the rank of each row returned from the query relative to other rows returned by the query, based onorder_by_clauseinvalue_exprs.
Syntax
/*Aggregate syntax*/
RANK(expr [, expr ]...) WITHIN GROUP
( ORDER BY
expr_col [ DESC | ASC ][ NULLS { FIRST | LAST } ]
[, expr_col [ DESC | ASC ][ NULLS { FIRST | LAST } ]]...
)
/*Analytic syntax*/
RANK() OVER ([ query_partition_clause ] order_by_clause)
Parameters
| Parameter | Description |
|---|---|
| expr | The value to query. |
| expr_col | The column name of the value to query. |
| DESC | ASC | Optional. The sorting method of the list.
|
| NULLS { FIRST | LAST } | Optional. The position of NULL in expr_col after sorting.
|
| OVER | You can use the OVER clause to define a window over the data on which the function operates. For more information, see Analytic functions. |
Return type
The return type is NUMBER.
Examples
The table emp_msg 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
Example of an aggregate function
Return the rank of 3300 in the sal column.
obclient> SELECT RANK(3300) WITHIN GROUP (ORDER BY sal) FROM emp_msg;
+-----------------------------------+
| RANK(3300)WITHINGROUP(ORDERBYSAL) |
+-----------------------------------+
| 13 |
+-----------------------------------+
1 row in set
Example of an analytic function
Group the data records in the table by the deptno column and sort the data records by the sal column in descending order. Return the rank of each value in the sal column.
obclient> SELECT deptno,ename,sal,
RANK() OVER (PARTITION BY deptno ORDER BY sal DESC) "RANK"
FROM emp_msg;
+--------+--------+------+------+
| DEPTNO | ENAME | SAL | RANK |
+--------+--------+------+------+
| 10 | KING | 5300 | 1 |
| 10 | CLARK | 2750 | 2 |
| 10 | MILLER | 1600 | 3 |
| 20 | FORD | 3300 | 1 |
| 20 | SCOTT | 3300 | 1 |
| 20 | JONES | 3275 | 3 |
| 20 | ADAMS | 1400 | 4 |
| 20 | SMITH | 1100 | 5 |
| 30 | BLAKE | 3150 | 1 |
| 30 | ALLEN | 1900 | 2 |
| 30 | TURNER | 1800 | 3 |
| 30 | SCLARK | 1750 | 4 |
| 30 | MARTIN | 1550 | 5 |
| 30 | WARD | 1550 | 5 |
| 30 | JAMES | 1250 | 7 |
+--------+--------+------+------+
15 rows in set