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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 value('039480001X', 1608, 1, 59, '1957-03-01', 'h');
postgres=# insert into editions value('0451160916', 7808, 1, 75, '1981-08-01', 'p');
postgres=# insert into editions value('0394800753', 1590, 1, 59, '1949-03-01', 'p');
postgres=# insert into editions value('0590445065', 25908, 1, 150, '1987-03-01', 'p');
postgres=# insert into editions value('0694003611', 1501, 1, 65, '1947-03-04', 'p');
postgres=# insert into editions value('0679803335', 1234, 1, 102, '1922-01-01', 'p');
postgres=# insert into editions value('0760720002', 190, 1, 91, '1868-01-01', 'p');
postgres=# insert into editions value('0394900014', 1608, 1, 59, '1957-01-01', 'p');
postgres=# insert into editions value('0385121679', 7808, 2, 75, '1993-10-01', 'h');
postgres=# insert into editions value('1885418035', 156, 1, 163, '1995-03-28', 'p');
postgres=# insert into editions value('0929605942', 156, 2, 171, '1998-12-01', 'p');
postgres=# insert into editions value('0441172717', 4513, 2, 99, '1998-09-01', 'p');
postgres=# insert into editions value('044100590X', 4513, 3, 99, '1999-10-01', 'h');
postgres=# insert into editions value('0451457994', 4267, 3, 101, '2000-09-12', 'p');
postgres=# insert into editions value('0451198492', 4267, 3, 101, '1999-10-01', 'h');
postgres=# insert into editions value('0823015505', 2038, 1, 62, '1958-01-01', 'p');
postgres=# insert into editions value('0596000855', 41473, 2, 113, '2001-03-01', 'p');
postgres=#
postgres=# select * from editions;
isbn | book_id | edition | publisher_id | publication | type
------+---------+---------+--------------+-------------+------
(0 rows)
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=# drop function stock_amount(integer, integer);
DROP FUNCTION
postgres=#
postgres=# -- Using the IF/THEN statement
postgres=#
postgres=# CREATE FUNCTION stock_amount (integer, integer) RETURNS integer AS '
postgres'# DECLARE
postgres'# -- Declare aliases for function arguments.
postgres'# b_id ALIAS FOR $1;
postgres'# b_edition ALIAS FOR $2;
postgres'# -- Declare variable to store the ISBN number.
postgres'# b_isbn TEXT;
postgres'# -- Declare variable to store the stock amount.
postgres'# stock_amount INTEGER;
postgres'# BEGIN
postgres'# SELECT INTO b_isbn isbn FROM editions WHERE
postgres'# book_id = b_id AND edition = b_edition;
postgres'#
postgres'# IF b_isbn IS NULL THEN
postgres'# RETURN -1;
postgres'# END IF;
postgres'#
postgres'# SELECT INTO stock_amount stock FROM stock WHERE isbn = b_isbn;
postgres'#
postgres'# RETURN stock_amount;
postgres'# END;
postgres'# ' LANGUAGE 'plpgsql';
CREATE FUNCTION
postgres=#
postgres=#
postgres=# SELECT stock_amount(7808,1);
stock_amount
--------------
-1
(1 row)
postgres=#
postgres=# drop table stock;
DROP TABLE
postgres=#
postgres=#
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