PostgreSQL/Table Joins/INNER JOIN

Comparing INNER JOIN to WHERE

postgres=#
postgres=# CREATE TABLE "books" (
postgres(#      "id"           integer NOT NULL,
postgres(#      "title"        text NOT NULL,
postgres(#      "author_id"    integer,
postgres(#      "subject_id"   integer,
postgres(#      Constraint "books_id_pkey" Primary Key ("id")
postgres(# );
NOTICE:  CREATE TABLE / PRIMARY KEY will create implicit index "books_id_pkey" for table "books"
CREATE TABLE
postgres=#
postgres=#
postgres=# insert into books values (7808,  "Java",                  4156, 9);
INSERT 0 1
postgres=# insert into books values (4513,  "Javascript",            1866, 15);
INSERT 0 1
postgres=# insert into books values (4267,  "C#",                    2001, 15);
INSERT 0 1
postgres=# insert into books values (1608,  "Oracle",                1809, 2);
INSERT 0 1
postgres=# insert into books values (1590,  "Sql Server",            1809, 2);
INSERT 0 1
postgres=# insert into books values (25908, "Postgre SQL",          15990, 2);
INSERT 0 1
postgres=# insert into books values (1501,  "Python",                2031, 2);
INSERT 0 1
postgres=# insert into books values (190,   "Java by API",             16, 6);
INSERT 0 1
postgres=# insert into books values (1234,  "2D",                   25041, 3);
INSERT 0 1
postgres=# insert into books values (2038,  "C",                     1644, 0);
INSERT 0 1
postgres=# insert into books values (156,   "C++",                    115, 9);
INSERT 0 1
postgres=# insert into books values (41473, "Programming Python",    7805, 4);
INSERT 0 1
postgres=# insert into books values (41477, "Learning Python",       7805, 4);
INSERT 0 1
postgres=# insert into books values (41478, "Perl Cookbook",         7806, 4);
INSERT 0 1
postgres=# insert into books values (41472, "Practical PostgreSQL",  1212, 4);
INSERT 0 1
postgres=#
postgres=# select * from books;
  id   |        title         | author_id | subject_id
-------+----------------------+-----------+------------
  7808 | Java                 |      4156 |          9
  4513 | Javascript           |      1866 |         15
  4267 | C#                   |      2001 |         15
  1608 | Oracle               |      1809 |          2
  1590 | Sql Server           |      1809 |          2
 25908 | Postgre SQL          |     15990 |          2
  1501 | Python               |      2031 |          2
   190 | Java by API          |        16 |          6
  1234 | 2D                   |     25041 |          3
  2038 | C                    |      1644 |          0
   156 | C++                  |       115 |          9
 41473 | Programming Python   |      7805 |          4
 41477 | Learning Python      |      7805 |          4
 41478 | Perl Cookbook        |      7806 |          4
 41472 | Practical PostgreSQL |      1212 |          4
(15 rows)
postgres=#
postgres=# CREATE TABLE "authors" (
postgres(#      "id" integer NOT NULL,
postgres(#      "last_name" text,
postgres(#      "first_name" text,
postgres(#      Constraint "authors_pkey" Primary Key ("id")
postgres(# );
NOTICE:  CREATE TABLE / PRIMARY KEY will create implicit index "authors_pkey" for table "authors"
CREATE TABLE
postgres=#
postgres=#
postgres=# insert into authors values (1111,  "Martin",       "Jason");
INSERT 0 1
postgres=# insert into authors values (1212,  "Worsley",      "Robert");
INSERT 0 1
postgres=# insert into authors values (15990, "Mathews",      "John");
INSERT 0 1
postgres=# insert into authors values (25041, "Smith",       "Williams");
INSERT 0 1
postgres=# insert into authors values (16,    "Alcott",       "May");
INSERT 0 1
postgres=# insert into authors values (4156,  "King",         "Stephen");
INSERT 0 1
postgres=# insert into authors values (1866,  "Herbert",      "Margaret");
INSERT 0 1
postgres=# insert into authors values (1644,  "Hogarth",      "Celia");
INSERT 0 1
postgres=# insert into authors values (2031,  "Brown",        "Wise");
INSERT 0 1
postgres=# insert into authors values (115,   "Poe",          "Allen");
INSERT 0 1
postgres=# insert into authors values (7805,  "Lutz",         "Mark");
INSERT 0 1
postgres=# insert into authors values (7806,  "Rice",         "Tom");
INSERT 0 1
postgres=# insert into authors values (1533,  "Black",        "Chris");
INSERT 0 1
postgres=# insert into authors values (1717,  "Brite",        "Linda");
INSERT 0 1
postgres=# insert into authors values (2112,  "Larry",        "Edward");
INSERT 0 1
postgres=# insert into authors values (2001,  "Clarke",       "Alison");
INSERT 0 1
postgres=# insert into authors values (1213,  "Green",        "Mary");
INSERT 0 1
postgres=#
postgres=# select * from authors;
  id   | last_name | first_name
-------+-----------+------------
  1111 | Martin    | Jason
  1212 | Worsley   | Robert
 15990 | Mathews   | John
 25041 | Smith     | Williams
    16 | Alcott    | May
  4156 | King      | Stephen
  1866 | Herbert   | Margaret
  1644 | Hogarth   | Celia
  2031 | Brown     | Wise
   115 | Poe       | Allen
  7805 | Lutz      | Mark
  7806 | Rice      | Tom
  1533 | Black     | Chris
  1717 | Brite     | Linda
  2112 | Larry     | Edward
  2001 | Clarke    | Alison
  1213 | Green     | Mary
(17 rows)
postgres=#
postgres=# -- Comparing INNER JOIN to WHERE
postgres=#
postgres=# SELECT title, last_name, first_name
postgres-#         FROM books, authors
postgres-#         WHERE (books.author_id = authors.id)
postgres-#         AND last_name = "Geisel";
 title | last_name | first_name
-------+-----------+------------
(0 rows)
postgres=#
postgres=#
postgres=#
postgres=#
postgres=# drop table authors;
DROP TABLE
postgres=# drop table books;
DROP TABLE
postgres=#
postgres=#

INNER JOIN two tables

postgres=#
postgres=# CREATE TABLE "books" (
postgres(#      "id"           integer NOT NULL,
postgres(#      "title"        text NOT NULL,
postgres(#      "author_id"    integer,
postgres(#      "subject_id"   integer,
postgres(#      Constraint "books_id_pkey" Primary Key ("id")
postgres(# );
NOTICE:  CREATE TABLE / PRIMARY KEY will create implicit index "books_id_pkey" for table "books"
CREATE TABLE
postgres=#
postgres=#
postgres=# insert into books values (7808,  "Java",                  4156, 9);
INSERT 0 1
postgres=# insert into books values (4513,  "Javascript",            1866, 15);
INSERT 0 1
postgres=# insert into books values (4267,  "C#",                    2001, 15);
INSERT 0 1
postgres=# insert into books values (1608,  "Oracle",                1809, 2);
INSERT 0 1
postgres=# insert into books values (1590,  "Sql Server",            1809, 2);
INSERT 0 1
postgres=# insert into books values (25908, "Postgre SQL",          15990, 2);
INSERT 0 1
postgres=# insert into books values (1501,  "Python",                2031, 2);
INSERT 0 1
postgres=# insert into books values (190,   "Java by API",             16, 6);
INSERT 0 1
postgres=# insert into books values (1234,  "2D",                   25041, 3);
INSERT 0 1
postgres=# insert into books values (2038,  "C",                     1644, 0);
INSERT 0 1
postgres=# insert into books values (156,   "C++",                    115, 9);
INSERT 0 1
postgres=# insert into books values (41473, "Programming Python",    7805, 4);
INSERT 0 1
postgres=# insert into books values (41477, "Learning Python",       7805, 4);
INSERT 0 1
postgres=# insert into books values (41478, "Perl Cookbook",         7806, 4);
INSERT 0 1
postgres=# insert into books values (41472, "Practical PostgreSQL",  1212, 4);
INSERT 0 1
postgres=#
postgres=# select * from books;
  id   |        title         | author_id | subject_id
-------+----------------------+-----------+------------
  7808 | Java                 |      4156 |          9
  4513 | Javascript           |      1866 |         15
  4267 | C#                   |      2001 |         15
  1608 | Oracle               |      1809 |          2
  1590 | Sql Server           |      1809 |          2
 25908 | Postgre SQL          |     15990 |          2
  1501 | Python               |      2031 |          2
   190 | Java by API          |        16 |          6
  1234 | 2D                   |     25041 |          3
  2038 | C                    |      1644 |          0
   156 | C++                  |       115 |          9
 41473 | Programming Python   |      7805 |          4
 41477 | Learning Python      |      7805 |          4
 41478 | Perl Cookbook        |      7806 |          4
 41472 | Practical PostgreSQL |      1212 |          4
(15 rows)
postgres=#
postgres=# CREATE TABLE "authors" (
postgres(#      "id" integer NOT NULL,
postgres(#      "last_name" text,
postgres(#      "first_name" text,
postgres(#      Constraint "authors_pkey" Primary Key ("id")
postgres(# );
NOTICE:  CREATE TABLE / PRIMARY KEY will create implicit index "authors_pkey" for table "authors"
CREATE TABLE
postgres=#
postgres=#
postgres=# insert into authors values (1111,  "Martin",       "Jason");
INSERT 0 1
postgres=# insert into authors values (1212,  "Worsley",      "Robert");
INSERT 0 1
postgres=# insert into authors values (15990, "Mathews",      "John");
INSERT 0 1
postgres=# insert into authors values (25041, "Smith",       "Williams");
INSERT 0 1
postgres=# insert into authors values (16,    "Alcott",       "May");
INSERT 0 1
postgres=# insert into authors values (4156,  "King",         "Stephen");
INSERT 0 1
postgres=# insert into authors values (1866,  "Herbert",      "Margaret");
INSERT 0 1
postgres=# insert into authors values (1644,  "Hogarth",      "Celia");
INSERT 0 1
postgres=# insert into authors values (2031,  "Brown",        "Wise");
INSERT 0 1
postgres=# insert into authors values (115,   "Poe",          "Allen");
INSERT 0 1
postgres=# insert into authors values (7805,  "Lutz",         "Mark");
INSERT 0 1
postgres=# insert into authors values (7806,  "Rice",         "Tom");
INSERT 0 1
postgres=# insert into authors values (1533,  "Black",        "Chris");
INSERT 0 1
postgres=# insert into authors values (1717,  "Brite",        "Linda");
INSERT 0 1
postgres=# insert into authors values (2112,  "Larry",        "Edward");
INSERT 0 1
postgres=# insert into authors values (2001,  "Clarke",       "Alison");
INSERT 0 1
postgres=#
postgres=# select * from authors;
  id   | last_name | first_name
-------+-----------+------------
  1111 | Martin    | Jason
  1212 | Worsley   | Robert
 15990 | Mathews   | John
 25041 | Smith     | Williams
    16 | Alcott    | May
  4156 | King      | Stephen
  1866 | Herbert   | Margaret
  1644 | Hogarth   | Celia
  2031 | Brown     | Wise
   115 | Poe       | Allen
  7805 | Lutz      | Mark
  7806 | Rice      | Tom
  1533 | Black     | Chris
  1717 | Brite     | Linda
  2112 | Larry     | Edward
  2001 | Clarke    | Alison
(16 rows)
postgres=#
postgres=# SELECT title, last_name, first_name
postgres-#         FROM books AS b INNER JOIN authors AS a
postgres-#         ON (b.author_id = a.id)
postgres-#         WHERE last_name = "Green";
 title | last_name | first_name
-------+-----------+------------
(0 rows)
postgres=#
postgres=#
postgres=#
postgres=#
postgres=# drop table authors;
DROP TABLE
postgres=# drop table books;
DROP TABLE
postgres=#
postgres=#

INNER JOIN two tables (2)

postgres=#
postgres=# CREATE TABLE t1 (
postgres(#     num         int,
postgres(#     name       varchar(10)
postgres(# );
CREATE TABLE
postgres=#
postgres=# insert into t1 values(1,"a");
INSERT 0 1
postgres=# insert into t1 values(2,"b");
INSERT 0 1
postgres=# insert into t1 values(3,"c");
INSERT 0 1
postgres=#
postgres=# CREATE TABLE t2 (
postgres(#     num         int,
postgres(#     name       varchar(10)
postgres(# );
CREATE TABLE
postgres=#
postgres=# insert into t2 values(1,"xxx");
INSERT 0 1
postgres=# insert into t2 values(3,"yyy");
INSERT 0 1
postgres=# insert into t2 values(5,"zzz");
INSERT 0 1
postgres=#
postgres=# SELECT * FROM t1 INNER JOIN t2 ON t1.num = t2.num;
 num | name | num | name
-----+------+-----+------
   1 | a    |   1 | xxx
   3 | c    |   3 | yyy
(2 rows)
postgres=#
postgres=# drop table t1;
DROP TABLE
postgres=# drop table t2;
DROP TABLE
postgres=#

INNER JOIN two tables USING (a column)

postgres=#
postgres=#
postgres=# CREATE TABLE t1 (
postgres(#     num         int,
postgres(#     name       varchar(10)
postgres(# );
CREATE TABLE
postgres=#
postgres=# insert into t1 values(1,"a");
INSERT 0 1
postgres=# insert into t1 values(2,"b");
INSERT 0 1
postgres=# insert into t1 values(3,"c");
INSERT 0 1
postgres=#
postgres=# CREATE TABLE t2 (
postgres(#     num         int,
postgres(#     name       varchar(10)
postgres(# );
CREATE TABLE
postgres=#
postgres=# insert into t2 values(1,"xxx");
INSERT 0 1
postgres=# insert into t2 values(3,"yyy");
INSERT 0 1
postgres=# insert into t2 values(5,"zzz");
INSERT 0 1
postgres=#
postgres=# SELECT * FROM t1 INNER JOIN t2 USING (num);
 num | name | name
-----+------+------
   1 | a    | xxx
   3 | c    | yyy
(2 rows)
postgres=#
postgres=# drop table t1;
DROP TABLE
postgres=# drop table t2;
DROP TABLE
postgres=#

Using GROUP BY with inner join

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(#      CONSTRAINT "integrity" CHECK (((book_id NOTNULL) AND (edition NOTNULL))),
postgres(#      Constraint "pkey" Primary Key ("isbn")
postgres(# );
NOTICE:  CREATE TABLE / PRIMARY KEY will create implicit index "pkey" for table "editions"
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(# );
NOTICE:  CREATE TABLE / PRIMARY KEY will create implicit index "publishers_pkey" for table "publishers"
CREATE TABLE
postgres=#
postgres=#
postgres=# insert into publishers values(150, "Can Press",  "29 Ave. Toronto, ON");
INSERT 0 1
postgres=# insert into publishers values(91,  "Henry Inc.", "115 Street New York, NY");
INSERT 0 1
postgres=# insert into publishers values(113, "O Inc.",     "101 St, Sebastopol, CA");
INSERT 0 1
postgres=# insert into publishers values(62,  "W Pubs",     "1515, New York");
INSERT 0 1
postgres=# insert into publishers values(105, "N Press",    "19 W, New York");
INSERT 0 1
postgres=# insert into publishers values(99,  "A Inc",      "375 St, New York");
INSERT 0 1
postgres=# insert into publishers values(101, "Z Inc",      "375 Ave, New York");
INSERT 0 1
postgres=# insert into publishers values(163, "M Press",    "PO Box 1215");
INSERT 0 1
postgres=# insert into publishers values(171, "B",          "16 W. 18th St. New York");
INSERT 0 1
postgres=# insert into publishers values(102, "P Inc",      "375 Hudson St, New York");
INSERT 0 1
postgres=# insert into publishers values(75,  "D Inc",      "1540 Broadway, New York");
INSERT 0 1
postgres=# insert into publishers values(65,  "H Pubs",     "10 E 53rd St, New York");
INSERT 0 1
postgres=# insert into publishers values(59,  "R Inc",      "1540 Broadway, New York");
INSERT 0 1
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=#
postgres=# --Using GROUP BY
postgres=#
postgres=# SELECT count(e.isbn) AS "number of books",
postgres-#         p.name AS publisher
postgres-#         FROM editions AS e INNER JOIN publishers AS p
postgres-#              ON (e.publisher_id = p.id)
postgres-#         GROUP BY p.name;
 number of books | publisher
-----------------+------------
               1 | B
               2 | D Inc
               1 | O Inc.
               2 | A Inc
               1 | H Pubs
               1 | W Pubs
               1 | P Inc
               2 | Z Inc
               1 | Can Press
               3 | R Inc
               1 | M Press
               1 | Henry Inc.
(12 rows)
postgres=#
postgres=# drop table editions cascade;
DROP TABLE
postgres=# drop table publisher cascade;
ERROR:  table "publisher" does not exist
postgres=#