|
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=# -- Using the FOR loop with %ROWTYPE
postgres=#
postgres=# CREATE FUNCTION extract_title (integer) RETURNS text AS '
postgres'# DECLARE
postgres'#
postgres'# -- Declare an alias for function argument.
postgres'# sub_id ALIAS FOR $1;
postgres'#
postgres'# -- Declare a variable to hold book titles and set its default
postgres'# -- value to a new line.
postgres'# text_output TEXT :=''\n'';
postgres'#
postgres'# -- Declare a variable to hold rows from the
postgres'# -- books table.
postgres'# row_data books%ROWTYPE;
postgres'#
postgres'# BEGIN
postgres'#
postgres'# -- Iterate through the results of a query.
postgres'# FOR row_data IN SELECT * FROM books
postgres'# WHERE subject_id = sub_id ORDER BY title LOOP
postgres'#
postgres'# -- Insert the title of a matching book into the text_output variable.
postgres'# text_output := text_output || row_data.title || ''\n'';
postgres'# END LOOP;
postgres'#
postgres'# -- Return the list of books.
postgres'# RETURN text_output;
postgres'# END;
postgres'# ' LANGUAGE 'plpgsql';
ERROR: function "extract_title" already exists with same argument types
postgres=#
postgres=#
postgres=# SELECT extract_title(2);
extract_title
---------------
Sql Server
(1 row)
postgres=#
postgres=#
postgres=# drop table books;
DROP TABLE
postgres=#
postgres=#
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