Mega Code Archive

Using the IFTHENELSE statement

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(# ); ERROR: relation "editions" already exists postgres=# postgres=# insert into editions values('039480001X', 1608, 1, 59, '1957-03-01', 'h'); ERROR: duplicate key violates unique constraint "pkey" postgres=# insert into editions values('0451160916', 7808, 1, 75, '1981-08-01', 'p'); ERROR: duplicate key violates unique constraint "pkey" postgres=# insert into editions values('0394800753', 1590, 1, 59, '1949-03-01', 'p'); ERROR: duplicate key violates unique constraint "pkey" postgres=# insert into editions values('0590445065', 25908, 1, 150, '1987-03-01', 'p'); ERROR: duplicate key violates unique constraint "pkey" postgres=# insert into editions values('0694003611', 1501, 1, 65, '1947-03-04', 'p'); ERROR: duplicate key violates unique constraint "pkey" postgres=# insert into editions values('0679803335', 1234, 1, 102, '1922-01-01', 'p'); ERROR: duplicate key violates unique constraint "pkey" postgres=# insert into editions values('0760720002', 190, 1, 91, '1868-01-01', 'p'); ERROR: duplicate key violates unique constraint "pkey" postgres=# insert into editions values('0394900014', 1608, 1, 59, '1957-01-01', 'p'); ERROR: duplicate key violates unique constraint "pkey" postgres=# insert into editions values('0385121679', 7808, 2, 75, '1993-10-01', 'h'); ERROR: duplicate key violates unique constraint "pkey" postgres=# insert into editions values('1885418035', 156, 1, 163, '1995-03-28', 'p'); ERROR: duplicate key violates unique constraint "pkey" postgres=# insert into editions values('0929605942', 156, 2, 171, '1998-12-01', 'p'); ERROR: duplicate key violates unique constraint "pkey" postgres=# insert into editions values('0441172717', 4513, 2, 99, '1998-09-01', 'p'); ERROR: duplicate key violates unique constraint "pkey" postgres=# insert into editions values('044100590X', 4513, 3, 99, '1999-10-01', 'h'); ERROR: duplicate key violates unique constraint "pkey" postgres=# insert into editions values('0451457994', 4267, 3, 101, '2000-09-12', 'p'); ERROR: duplicate key violates unique constraint "pkey" postgres=# insert into editions values('0451198492', 4267, 3, 101, '1999-10-01', 'h'); ERROR: duplicate key violates unique constraint "pkey" postgres=# insert into editions values('0823015505', 2038, 1, 62, '1958-01-01', 'p'); ERROR: duplicate key violates unique constraint "pkey" postgres=# insert into editions values('0596000855', 41473, 2, 113, '2001-03-01', 'p'); ERROR: duplicate key violates unique constraint "pkey" 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=# postgres=# -- Using the IF/THEN/ELSE statement postgres=# postgres=# CREATE FUNCTION in_stock (integer,integer) RETURNS boolean AS ' postgres'# DECLARE postgres'# -- Declare aliases for function arguments. postgres'# b_id ALIAS FOR $1; postgres'# b_edition ALIAS FOR $2; postgres'# postgres'# -- Declare a text variable to hold the ISBN of the book postgres'# -- once found. postgres'# b_isbn TEXT; postgres'# postgres'# -- Declare an integer variable to hold the amount of stock. postgres'# stock_amount INTEGER; postgres'# postgres'# BEGIN postgres'# 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 FALSE; postgres'# END IF; postgres'# postgres'# SELECT INTO stock_amount stock FROM stock WHERE isbn = b_isbn; postgres'# postgres'# IF stock_amount <= 0 THEN postgres'# RETURN FALSE; postgres'# ELSE postgres'# RETURN TRUE; postgres'# END IF; postgres'# postgres'# END; postgres'# ' LANGUAGE 'plpgsql'; CREATE FUNCTION postgres=# postgres=# postgres=# SELECT in_stock(4513,2); in_stock ---------- t (1 row) postgres=# postgres=# postgres=# drop table editions; DROP TABLE postgres=#