128 lines
3.2 KiB
Plaintext
128 lines
3.2 KiB
Plaintext
---------------------------------------------------------------------------
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--
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-- advanced.sql-
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-- more POSTGRES SQL features. (These are not part of the SQL-92
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-- standard.)
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--
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--
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-- Copyright (c) 1994, Regents of the University of California
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--
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-- $Id: advanced.source,v 1.3 1999/07/08 15:28:51 momjian Exp $
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--
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---------------------------------------------------------------------------
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-----------------------------
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-- Inheritance:
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-- a table can inherit from zero or more tables. A query can reference
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-- either all rows of a table or all rows of a table plus all of its
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-- descendants.
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-----------------------------
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-- For example, the capitals table inherits from cities table. (It inherits
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-- all data fields from cities.)
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CREATE TABLE cities (
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name text,
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population float8,
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altitude int -- (in ft)
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);
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CREATE TABLE capitals (
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state char(2)
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) INHERITS (cities);
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-- now, let's populate the tables
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INSERT INTO cities VALUES ('San Francisco', 7.24E+5, 63);
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INSERT INTO cities VALUES ('Las Vegas', 2.583E+5, 2174);
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INSERT INTO cities VALUES ('Mariposa', 1200, 1953);
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INSERT INTO capitals VALUES ('Sacramento', 3.694E+5, 30, 'CA');
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INSERT INTO capitals VALUES ('Madison', 1.913E+5, 845, 'WI');
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SELECT * FROM cities;
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SELECT * FROM capitals;
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-- like before, a regular query references rows of the base table only
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SELECT name, altitude
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FROM cities
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WHERE altitude > 500;
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-- on the other hand, you can find all cities, including capitals, that
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-- are located at an altitude of 500 'ft or higher by:
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SELECT c.name, c.altitude
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FROM cities* c
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WHERE c.altitude > 500;
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-----------------------------
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-- Time Travel:
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-- this feature allows you to run historical queries.
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-- removed for v6.3, but possible using triggers.
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-- see contrib/spi/README for more information.
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-----------------------------
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-- first, let's make some changes to the cities table (suppose Mariposa's
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-- population grows 10% this year)
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-- UPDATE cities
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-- SET population = population * 1.1
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-- WHERE name = 'Mariposa';
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-- the default time is the current time ('now'):
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-- SELECT * FROM cities WHERE name = 'Mariposa';
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-- we can also retrieve the population of Mariposa ever has. ('epoch' is the
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-- earliest time representable by the system)
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-- SELECT name, population
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-- FROM cities['epoch', 'now'] -- can be abbreviated to cities[,]
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-- WHERE name = 'Mariposa';
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----------------------
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-- Arrays:
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-- attributes can be arrays of base types or user-defined types
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----------------------
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CREATE TABLE sal_emp (
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name text,
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pay_by_quarter int4[],
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schedule text[][]
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);
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-- insert instances with array attributes. Note the use of braces
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INSERT INTO sal_emp VALUES (
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'Bill',
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'{10000,10000,10000,10000}',
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'{{"meeting", "lunch"}, {}}');
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INSERT INTO sal_emp VALUES (
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'Carol',
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'{20000,25000,25000,25000}',
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'{{"talk", "consult"}, {"meeting"}}');
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----------------------
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-- queries on array attributes
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----------------------
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SELECT name FROM sal_emp WHERE
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sal_emp.pay_by_quarter[1] <> sal_emp.pay_by_quarter[2];
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-- retrieve third quarter pay of all employees
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SELECT sal_emp.pay_by_quarter[3] FROM sal_emp;
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-- select subarrays
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SELECT sal_emp.schedule[1:2][1:1] FROM sal_emp WHERE
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sal_emp.name = 'Bill';
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-- clean up (you must remove the children first)
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DROP TABLE sal_emp;
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DROP TABLE capitals;
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DROP TABLE cities;
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