diff --git a/doc/src/sgml/advanced.sgml b/doc/src/sgml/advanced.sgml index 755c9f14850..e15a3323dfb 100644 --- a/doc/src/sgml/advanced.sgml +++ b/doc/src/sgml/advanced.sgml @@ -389,30 +389,32 @@ SELECT depname, empno, salary, avg(salary) OVER (PARTITION BY depname) FROM emps SELECT depname, empno, salary, - rank() OVER (PARTITION BY depname ORDER BY salary DESC) + row_number() OVER (PARTITION BY depname ORDER BY salary DESC) FROM empsalary; - depname | empno | salary | rank ------------+-------+--------+------ - develop | 8 | 6000 | 1 - develop | 10 | 5200 | 2 - develop | 11 | 5200 | 2 - develop | 9 | 4500 | 4 - develop | 7 | 4200 | 5 - personnel | 2 | 3900 | 1 - personnel | 5 | 3500 | 2 - sales | 1 | 5000 | 1 - sales | 4 | 4800 | 2 - sales | 3 | 4800 | 2 + depname | empno | salary | row_number +-----------+-------+--------+------------ + develop | 8 | 6000 | 1 + develop | 10 | 5200 | 2 + develop | 11 | 5200 | 3 + develop | 9 | 4500 | 4 + develop | 7 | 4200 | 5 + personnel | 2 | 3900 | 1 + personnel | 5 | 3500 | 2 + sales | 1 | 5000 | 1 + sales | 4 | 4800 | 2 + sales | 3 | 4800 | 3 (10 rows) - As shown here, the rank function produces a numerical rank - for each distinct ORDER BY value in the current row's - partition, using the order defined by the ORDER BY clause. - rank needs no explicit parameter, because its behavior + As shown here, the row_number window function + assigns sequential numbers to the rows within each partition, + in the order defined by the ORDER BY clause + (with tied rows numbered in an unspecified order). + row_number needs no explicit parameter, + because its behavior is entirely determined by the OVER clause. @@ -527,14 +529,15 @@ SELECT salary, sum(salary) OVER (ORDER BY salary) FROM empsalary; SELECT depname, empno, salary, enroll_date FROM (SELECT depname, empno, salary, enroll_date, - rank() OVER (PARTITION BY depname ORDER BY salary DESC, empno) AS pos + row_number() OVER (PARTITION BY depname ORDER BY salary DESC, empno) AS pos FROM empsalary ) AS ss WHERE pos < 3; The above query only shows the rows from the inner query having - rank less than 3. + row_number less than 3 (that is, the first + two rows for each department). diff --git a/src/tutorial/advanced.source b/src/tutorial/advanced.source index 0c68b3344c3..f46fced1a5f 100644 --- a/src/tutorial/advanced.source +++ b/src/tutorial/advanced.source @@ -10,6 +10,55 @@ -- --------------------------------------------------------------------------- +----------------------------- +-- Window Functions +----------------------------- + +-- a sample table +CREATE TABLE empsalary ( + depname text, + empno bigint, + salary int, + enroll_date date +); + +INSERT INTO empsalary VALUES +('develop', 10, 5200, '2007-08-01'), +('sales', 1, 5000, '2006-10-01'), +('personnel', 5, 3500, '2007-12-10'), +('sales', 4, 4800, '2007-08-08'), +('personnel', 2, 3900, '2006-12-23'), +('develop', 7, 4200, '2008-01-01'), +('develop', 9, 4500, '2008-01-01'), +('sales', 3, 4800, '2007-08-01'), +('develop', 8, 6000, '2006-10-01'), +('develop', 11, 5200, '2007-08-15'); + +SELECT depname, empno, salary, avg(salary) OVER (PARTITION BY depname) + FROM empsalary; + +SELECT depname, empno, salary, + row_number() OVER (PARTITION BY depname ORDER BY salary DESC) +FROM empsalary; + +SELECT salary, sum(salary) OVER () FROM empsalary; + +SELECT salary, sum(salary) OVER (ORDER BY salary) FROM empsalary; + +SELECT depname, empno, salary, enroll_date +FROM + (SELECT depname, empno, salary, enroll_date, + row_number() OVER (PARTITION BY depname ORDER BY salary DESC, empno) AS pos + FROM empsalary + ) AS ss +WHERE pos < 3; + +SELECT sum(salary) OVER w, avg(salary) OVER w + FROM empsalary + WINDOW w AS (PARTITION BY depname ORDER BY salary DESC); + +DROP TABLE empsalary; + ----------------------------- -- Inheritance: -- A table can inherit from zero or more tables. A query can reference