Operate on a set of rows that rank as the FIRST or LAST with respect to a given sorting specification, in many cases only one row will rank as FIRST or
LAST.
Note that the value retrieved from the first or last row need not be from the column on which the group was sorted.
The FIRST and LAST functions eliminate the need for self joins or views and enable better performance.
Syntax
aggregate_function KEEP
(DENSE_RANK FIRST
ORDER BY Order_by_clause)
[OVER (query_partitioning_clause)]
aggregate_function KEEP
(DENSE_RANK LAST
ORDER BY Order_by_clause)
[OVER (query_partitioning_clause)]
Order by clause:
ORDER BY expr [ DESC | ASC ] [ NULLS { FIRST | LAST }]
[, expr [ DESC | ASC ] [ NULLS { FIRST | LAST }]]…
query_partitioning_clause:
PARTITION BY value/expr [,value/expr…]
Dense_Rank:
DENSE_RANK FIRST or DENSE_RANK LAST indicates that Oracle will aggregate over only those rows with the minimum (FIRST) or the maximum (LAST) dense rank ("olympic rank").
aggregate_functions:
Any one of MIN, MAX, SUM, AVG, COUNT, VARIANCE, or STDDEV.
The function will only operate on those rows that rank either FIRST or LAST (often a single row).
OVER
Specifying the OVER (PARTITION… clause will apply the FIRST and LAST functions as analytic functions (rather than as simple aggregate functions).
Example (aggregate function):
SELECT department_id,
MIN(salary) KEEP (DENSE_RANK FIRST ORDER BY commission_pct) "Worst",
MAX(salary) KEEP (DENSE_RANK LAST ORDER BY commission_pct) "Best"
FROM employees
GROUP BY department_id;
DEPARTMENT_ID Worst Best
------------- ---------- ----------
10 4400 4400
20 6000 13000
30 2500 11000
40 6500 6500
50 2100 8200
…
This displays the best and worst salary for employees in each department.
Example (analytic function):
For each employee within the department
SELECT last_name, department_id, salary,
MIN(salary) KEEP (DENSE_RANK FIRST ORDER BY commission_pct)
OVER (PARTITION BY department_id) "Worst",
MAX(salary) KEEP (DENSE_RANK LAST ORDER BY commission_pct)
OVER (PARTITION BY department_id) "Best"
FROM employees
ORDER BY department_id, salary;
LAST_NAME DEPARTMENT_ID SALARY Worst Best
------------------- ------------- ---------- ---------- ----------
Whalen 10 4400 4400 4400
Goyal 20 6000 6000 13000
Hartstein 20 13000 6000 13000
…
This displays the employees salary along with the best and worst salaries for all employees in the same dept.
“This is not the end. It is not even the beginning of the end. It is perhaps the end of the beginning” ~ Winston Churchill
Back to Analytic features
List of all functions