Using SUM function with natural join
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 "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=#
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=# CREATE TABLE "subjects" (
postgres(# "id" integer NOT NULL,
postgres(# "subject" text,
postgres(# "location" text,
postgres(# Constraint "subjects_pkey" Primary Key ("id")
postgres(# );
ERROR: relation "subjects" already exists
postgres=#
postgres=# insert into subjects values (0, 'Arts', 'Creativity St');
postgres=# insert into subjects values (1, 'Business', 'Productivity Ave');
postgres=# insert into subjects values (2, 'Children', 'Books Kids Ct');
INSERT 0 1
postgres=# insert into subjects values (3, 'Classics', 'Academic Rd');
INSERT 0 1
postgres=# insert into subjects values (4, 'Computers', 'Productivity Ave');
INSERT 0 1
postgres=# insert into subjects values (5, 'Cooking', 'Creativity St');
INSERT 0 1
postgres=# insert into subjects values (6, 'Drama', 'Main St');
INSERT 0 1
postgres=# insert into subjects values (7, 'Entertainment', 'Main St');
INSERT 0 1
postgres=# insert into subjects values (8, 'History', 'Academic Rd');
INSERT 0 1
postgres=# insert into subjects values (9, 'Horror', 'Black Raven Dr');
INSERT 0 1
postgres=# insert into subjects values (10, 'Mystery', 'Black Raven Dr');
INSERT 0 1
postgres=# insert into subjects values (11, 'Poetry', 'Sunset Dr');
INSERT 0 1
postgres=# insert into subjects values (12, 'Religion', 'Regina');
INSERT 0 1
postgres=# insert into subjects values (13, 'Romance', 'Main St');
INSERT 0 1
postgres=# insert into subjects values (14, 'Science', 'Productivity Ave');
INSERT 0 1
postgres=# insert into subjects values (15, 'Science Fiction', 'Main St');
INSERT 0 1
postgres=#
postgres=# select * from subjects;
id | subject | location
----+-----------------+------------------
0 | Arts | Creativity St
1 | Business | Productivity Ave
2 | Children | Books Kids Ct
3 | Classics | Academic Rd
4 | Computers | Productivity Ave
5 | Cooking | Creativity St
6 | Drama | Main St
7 | Entertainment | Main St
8 | History | Academic Rd
9 | Horror | Black Raven Dr
10 | Mystery | Black Raven Dr
11 | Poetry | Sunset Dr
12 | Religion | Regina
13 | Romance | Main St
14 | Science | Productivity Ave
15 | Science Fiction | Main St
(16 rows)
postgres=#
postgres=#
postgres=# SELECT sum(stock), s.subject
postgres-# FROM ((stock NATURAL JOIN editions)
postgres(# JOIN books ON (books.id = book_id))
postgres-# JOIN subjects AS s
postgres-# ON (books.subject_id = s.id)
postgres-# GROUP BY s.subject
postgres-# ORDER BY sum DESC;
sum | subject
-----+-----------------
189 | Horror
166 | Science Fiction
95 | Children
28 | Drama
18 | Classics
16 | Arts
(6 rows)
postgres=#
postgres=# drop table editions;
DROP TABLE
postgres=# drop table books;
DROP TABLE
postgres=# drop table stock;
DROP TABLE
postgres=#
| 1. | SUM for a 'real' value |