Using the IF/THEN/ELSE statement : If « Postgre SQL « PostgreSQL






Using the IF/THEN/ELSE 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=#
           
       








Related examples in the same category