PostgreSQL/Analytical Functions/Variance

Using variance function with natural join

postgres=#
postgres=#
postgres=#
postgres=# CREATE TABLE "stock" (
postgres(#      "isbn" text NOT NULL,
postgres(#      "cost" numeric(5,2),
postgres(#      "retail" numeric(5,2),
postgres(#      "stock" integer,
postgres(#      Constraint "stock_pkey" Primary Key ("isbn")
postgres(# );
NOTICE:  CREATE TABLE / PRIMARY KEY will create implicit index "stock_pkey" for table "stock"
CREATE TABLE
postgres=#
postgres=#
postgres=# insert into stock values ("0385121679", 29.00, 36.95, 65);
INSERT 0 1
postgres=# insert into stock values ("039480001X", 30.00, 32.95, 31);
INSERT 0 1
postgres=# insert into stock values ("0394900014", 23.00, 23.95, 0);
INSERT 0 1
postgres=# insert into stock values ("044100590X", 36.00, 45.95, 89);
INSERT 0 1
postgres=# insert into stock values ("0441172717", 17.00, 21.95, 77);
INSERT 0 1
postgres=# insert into stock values ("0451160916", 24.00, 28.95, 22);
INSERT 0 1
postgres=# insert into stock values ("0451198492", 36.00, 46.95, 0);
INSERT 0 1
postgres=# insert into stock values ("0451457994", 17.00, 22.95, 0);
INSERT 0 1
postgres=# insert into stock values ("0590445065", 23.00, 23.95, 10);
INSERT 0 1
postgres=# insert into stock values ("0679803335", 20.00, 24.95, 18);
INSERT 0 1
postgres=# insert into stock values ("0694003611", 25.00, 28.95, 50);
INSERT 0 1
postgres=# insert into stock values ("0760720002", 18.00, 23.95, 28);
INSERT 0 1
postgres=# insert into stock values ("0823015505", 26.00, 28.95, 16);
INSERT 0 1
postgres=# insert into stock values ("0929605942", 19.00, 21.95, 25);
INSERT 0 1
postgres=# insert into stock values ("1885418035", 23.00, 24.95, 77);
INSERT 0 1
postgres=# insert into stock values ("0394800753", 16.00, 16.95, 4);
INSERT 0 1
postgres=#
postgres=# select * FROM stock;
    isbn    | cost  | retail | stock
------------+-------+--------+-------
 0385121679 | 29.00 |  36.95 |    65
 039480001X | 30.00 |  32.95 |    31
 0394900014 | 23.00 |  23.95 |     0
 044100590X | 36.00 |  45.95 |    89
 0441172717 | 17.00 |  21.95 |    77
 0451160916 | 24.00 |  28.95 |    22
 0451198492 | 36.00 |  46.95 |     0
 0451457994 | 17.00 |  22.95 |     0
 0590445065 | 23.00 |  23.95 |    10
 0679803335 | 20.00 |  24.95 |    18
 0694003611 | 25.00 |  28.95 |    50
 0760720002 | 18.00 |  23.95 |    28
 0823015505 | 26.00 |  28.95 |    16
 0929605942 | 19.00 |  21.95 |    25
 1885418035 | 23.00 |  24.95 |    77
 0394800753 | 16.00 |  16.95 |     4
(16 rows)
postgres=#
postgres=#
postgres=# CREATE TABLE "editions" (
postgres(#      "isbn" text NOT NULL,
postgres(#      "book_id" integer,
postgres(#      "edition" integer,
postgres(#      "publisher_id" integer,
postgres(#      "publication" date,
postgres(#      "type" character(1)
postgres(# );
CREATE TABLE
postgres=#
postgres=# insert into editions values("039480001X", 1608,  1,  59,  "1957-03-01", "h");
INSERT 0 1
postgres=# insert into editions values("0451160916", 7808,  1,  75,  "1981-08-01", "p");
INSERT 0 1
postgres=# insert into editions values("0394800753", 1590,  1,  59,  "1949-03-01", "p");
INSERT 0 1
postgres=# insert into editions values("0590445065", 25908, 1,  150, "1987-03-01", "p");
INSERT 0 1
postgres=# insert into editions values("0694003611", 1501,  1,  65,  "1947-03-04", "p");
INSERT 0 1
postgres=# insert into editions values("0679803335", 1234,  1,  102, "1922-01-01", "p");
INSERT 0 1
postgres=# insert into editions values("0760720002", 190,   1,  91,  "1868-01-01", "p");
INSERT 0 1
postgres=# insert into editions values("0394900014", 1608,  1,  59,  "1957-01-01", "p");
INSERT 0 1
postgres=# insert into editions values("0385121679", 7808,  2,  75,  "1993-10-01", "h");
INSERT 0 1
postgres=# insert into editions values("1885418035", 156,   1,  163, "1995-03-28", "p");
INSERT 0 1
postgres=# insert into editions values("0929605942", 156,   2,  171, "1998-12-01", "p");
INSERT 0 1
postgres=# insert into editions values("0441172717", 4513,  2,  99,  "1998-09-01", "p");
INSERT 0 1
postgres=# insert into editions values("044100590X", 4513,  3,  99,  "1999-10-01", "h");
INSERT 0 1
postgres=# insert into editions values("0451457994", 4267,  3,  101, "2000-09-12", "p");
INSERT 0 1
postgres=# insert into editions values("0451198492", 4267,  3,  101, "1999-10-01", "h");
INSERT 0 1
postgres=# insert into editions values("0823015505", 2038,  1,  62,  "1958-01-01", "p");
INSERT 0 1
postgres=# insert into editions values("0596000855", 41473, 2,  113, "2001-03-01", "p");
INSERT 0 1
postgres=#
postgres=# select * from editions;
    isbn    | book_id | edition | publisher_id | publication | type
------------+---------+---------+--------------+-------------+------
 039480001X |    1608 |       1 |           59 | 1957-03-01  | h
 0451160916 |    7808 |       1 |           75 | 1981-08-01  | p
 0394800753 |    1590 |       1 |           59 | 1949-03-01  | p
 0590445065 |   25908 |       1 |          150 | 1987-03-01  | p
 0694003611 |    1501 |       1 |           65 | 1947-03-04  | p
 0679803335 |    1234 |       1 |          102 | 1922-01-01  | p
 0760720002 |     190 |       1 |           91 | 1868-01-01  | p
 0394900014 |    1608 |       1 |           59 | 1957-01-01  | p
 0385121679 |    7808 |       2 |           75 | 1993-10-01  | h
 1885418035 |     156 |       1 |          163 | 1995-03-28  | p
 0929605942 |     156 |       2 |          171 | 1998-12-01  | p
 0441172717 |    4513 |       2 |           99 | 1998-09-01  | p
 044100590X |    4513 |       3 |           99 | 1999-10-01  | h
 0451457994 |    4267 |       3 |          101 | 2000-09-12  | p
 0451198492 |    4267 |       3 |          101 | 1999-10-01  | h
 0823015505 |    2038 |       1 |           62 | 1958-01-01  | p
 0596000855 |   41473 |       2 |          113 | 2001-03-01  | p
(17 rows)
postgres=#
postgres=#
postgres=# CREATE TABLE "publishers" (
postgres(#      "id" integer NOT NULL,
postgres(#      "name" text,
postgres(#      "address" text,
postgres(#      Constraint "publishers_pkey" Primary Key ("id")
postgres(# );
postgres=#
postgres=#
postgres=# insert into publishers values(150, "Can Press",  "29 Ave. Toronto, ON");
postgres=# insert into publishers values(91,  "Henry Inc.", "115 Street New York, NY");
postgres=# insert into publishers values(113, "O Inc.",     "101 St, Sebastopol, CA");
postgres=# insert into publishers values(62,  "W Pubs",     "1515, New York");
postgres=# insert into publishers values(105, "N Press",    "19 W, New York");
postgres=# insert into publishers values(99,  "A Inc",      "375 St, New York");
postgres=# insert into publishers values(101, "Z Inc",      "375 Ave, New York");
postgres=# insert into publishers values(163, "M Press",    "PO Box 1215");
postgres=# insert into publishers values(171, "B",          "16 W. 18th St. New York");
postgres=# insert into publishers values(102, "P Inc",      "375 Hudson St, New York");
postgres=# insert into publishers values(75,  "D Inc",      "1540 Broadway, New York");
postgres=# insert into publishers values(65,  "H Pubs",     "10 E 53rd St, New York");
postgres=# insert into publishers values(59,  "R Inc",      "1540 Broadway, New York");
postgres=#
postgres=# select * from publishers;
 id  |    name    |         address
-----+------------+-------------------------
 150 | Can Press  | 29 Ave. Toronto, ON
  91 | Henry Inc. | 115 Street New York, NY
 113 | O Inc.     | 101 St, Sebastopol, CA
  62 | W Pubs     | 1515, New York
 105 | N Press    | 19 W, New York
  99 | A Inc      | 375 St, New York
 101 | Z Inc      | 375 Ave, New York
 163 | M Press    | PO Box 1215
 171 | B          | 16 W. 18th St. New York
 102 | P Inc      | 375 Hudson St, New York
  75 | D Inc      | 1540 Broadway, New York
  65 | H Pubs     | 10 E 53rd St, New York
  59 | R Inc      | 1540 Broadway, New York
(13 rows)
postgres=#
postgres=# SELECT variance(retail), p.name
postgres-#         FROM (stock NATURAL JOIN editions)
postgres-#         JOIN publishers AS p
postgres-#                         ON (editions.publisher_id = p.id)
postgres-#         GROUP BY p.name
postgres-#         ORDER BY variance DESC
postgres-#         LIMIT 4;
 variance |   name
----------+-----------
          | B
          | M Press
          | Can Press
          | H Pubs
(4 rows)
postgres=#
postgres=# drop table publisher;
ERROR:  table "publisher" does not exist
postgres=# drop table editions;
DROP TABLE
postgres=# drop table stock;
DROP TABLE
postgres=#

Variance function demo

postgres=#
postgres=#
postgres=# CREATE TABLE employee (
postgres(#     ID         int,
postgres(#     name       varchar(10),
postgres(#     salary     real,
postgres(#     start_date date,
postgres(#     city       varchar(10),
postgres(#     region     char(1)
postgres(# );
CREATE TABLE
postgres=#
postgres=# insert into employee (ID, name,    salary, start_date, city,       region)
postgres-#               values (1,  "Jason", 40420,  "02/01/94", "New York", "W");
INSERT 0 1
postgres=# insert into employee (ID, name,    salary, start_date, city,       region)
postgres-#               values (2,  "Robert",14420,  "01/02/95", "Vancouver","N");
INSERT 0 1
postgres=# insert into employee (ID, name,    salary, start_date, city,       region)
postgres-#               values (3,  "Celia", 24020,  "12/03/96", "Toronto",  "W");
INSERT 0 1
postgres=# insert into employee (ID, name,    salary, start_date, city,       region)
postgres-#               values (4,  "Linda", 40620,  "11/04/97", "New York", "N");
INSERT 0 1
postgres=# insert into employee (ID, name,    salary, start_date, city,       region)
postgres-#               values (5,  "David", 80026,  "10/05/98", "Vancouver","W");
INSERT 0 1
postgres=# insert into employee (ID, name,    salary, start_date, city,       region)
postgres-#               values (6,  "James", 70060,  "09/06/99", "Toronto",  "N");
INSERT 0 1
postgres=# insert into employee (ID, name,    salary, start_date, city,       region)
postgres-#               values (7,  "Alison",90620,  "08/07/00", "New York", "W");
INSERT 0 1
postgres=# insert into employee (ID, name,    salary, start_date, city,       region)
postgres-#               values (8,  "Chris", 26020,  "07/08/01", "Vancouver","N");
INSERT 0 1
postgres=# insert into employee (ID, name,    salary, start_date, city,       region)
postgres-#               values (9,  "Mary",  60020,  "06/09/02", "Toronto",  "W");
INSERT 0 1
postgres=#
postgres=# select * from employee;
 id |  name  | salary | start_date |   city    | region
----+--------+--------+------------+-----------+--------
  1 | Jason  |  40420 | 1994-02-01 | New York  | W
  2 | Robert |  14420 | 1995-01-02 | Vancouver | N
  3 | Celia  |  24020 | 1996-12-03 | Toronto   | W
  4 | Linda  |  40620 | 1997-11-04 | New York  | N
  5 | David  |  80026 | 1998-10-05 | Vancouver | W
  6 | James  |  70060 | 1999-09-06 | Toronto   | N
  7 | Alison |  90620 | 2000-08-07 | New York  | W
  8 | Chris  |  26020 | 2001-07-08 | Vancouver | N
  9 | Mary   |  60020 | 2002-06-09 | Toronto   | W
(9 rows)
postgres=#
postgres=# SELECT variance(salary) FROM employee;
 variance
-----------
 718558064
(1 row)
postgres=#
postgres=#
postgres=# drop table employee;
DROP TABLE
postgres=#