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New blood and fresh air for tutorial
This commit is contained in:
Peter Eisentraut
@ -1,19 +1,18 @@
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---------------------------------------------------------------------------
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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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-- Tutorial on advanced more PostgreSQL features
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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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-- $Id: advanced.source,v 1.4 2001/09/02 23:27:50 petere 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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-- S 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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@ -31,7 +30,7 @@ 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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-- 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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@ -56,72 +55,6 @@ 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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@ -6,22 +6,22 @@
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--
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-- Copyright (c) 1994, Andrew Yu, University of California
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--
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-- $Id: basics.source,v 1.3 1999/07/08 15:27:01 momjian Exp $
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-- $Id: basics.source,v 1.4 2001/09/02 23:27:50 petere Exp $
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--
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---------------------------------------------------------------------------
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-----------------------------
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-- Creating a table:
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-- a CREATE TABLE is used to create base tables. POSTGRES SQL has
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-- its own set of built-in types. (Note that keywords are case-
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-- insensitive but identifiers are case-sensitive.)
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-- Creating a New Table:
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-- A CREATE TABLE is used to create base tables. PostgreSQL has
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-- its own set of built-in types. (Note that SQL is case-
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-- insensitive.)
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-----------------------------
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CREATE TABLE weather (
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city varchar(80),
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temp_lo int, -- low temperature
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temp_hi int, -- high temperature
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prcp float8, -- precipitation
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prcp real, -- precipitation
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date date
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);
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@ -30,98 +30,105 @@ CREATE TABLE cities (
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location point
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);
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-----------------------------
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-- Inserting data:
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-- an INSERT statement is used to insert a new row into a table. There
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-- Populating a Table With Rows:
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-- An INSERT statement is used to insert a new row into a table. There
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-- are several ways you can specify what columns the data should go to.
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-----------------------------
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-- 1. the simplest case is when the list of value correspond to the order of
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-- 1. The simplest case is when the list of value correspond to the order of
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-- the columns specified in CREATE TABLE.
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INSERT INTO weather
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VALUES ('San Francisco', 46, 50, 0.25, '11/27/1994');
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VALUES ('San Francisco', 46, 50, 0.25, '1994-11-27');
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INSERT INTO cities
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VALUES ('San Francisco', '(-194.0, 53.0)');
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VALUES ('San Francisco', '(-194.0, 53.0)');
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-- 2. you can also specify what column the values correspond to. (The columns
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-- can be specified in any order. You may also omit any number of columns.
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-- eg. unknown precipitation below)
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-- 2. You can also specify what column the values correspond to. (The columns
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-- can be specified in any order. You may also omit any number of columns,
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-- e.g., unknown precipitation below.
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INSERT INTO weather (city, temp_lo, temp_hi, prcp, date)
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VALUES ('San Francisco', 43, 57, 0.0, '11/29/1994');
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VALUES ('San Francisco', 43, 57, 0.0, '1994-11-29');
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INSERT INTO weather (date, city, temp_hi, temp_lo)
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VALUES ('11/29/1994', 'Hayward', 54, 37);
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VALUES ('1994-11-29', 'Hayward', 54, 37);
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-----------------------------
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-- Retrieving data:
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-- a SELECT statement is used for retrieving data. The basic syntax is
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-- SELECT columns FROM tables WHERE predicates
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-- Querying a Table:
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-- A SELECT statement is used for retrieving data. The basic syntax is
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-- SELECT columns FROM tables WHERE predicates.
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-----------------------------
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-- a simple one would be
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-- A simple one would be:
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SELECT * FROM weather;
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-- you may also specify expressions in the target list (the 'AS column'
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-- specifies the column name of the result. It is optional.)
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-- You may also specify expressions in the target list. (The 'AS column'
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-- specifies the column name of the result. It is optional.)
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SELECT city, (temp_hi+temp_lo)/2 AS temp_avg, date FROM weather;
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-- if you want to retrieve rows that satisfy certain condition (ie. a
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-- restriction), specify the condition in WHERE. The following retrieves
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-- If you want to retrieve rows that satisfy certain condition (i.e., a
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-- restriction), specify the condition in WHERE. The following retrieves
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-- the weather of San Francisco on rainy days.
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SELECT *
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FROM weather
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WHERE city = 'San Francisco'
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and prcp > 0.0;
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FROM weather
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WHERE city = 'San Francisco'
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AND prcp > 0.0;
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-- here is a more complicated one. Duplicates are removed when DISTINCT is
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-- specified. ORDER BY specifies the column to sort on. (Just to make sure the
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-- Here is a more complicated one. Duplicates are removed when DISTINCT is
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-- specified. ORDER BY specifies the column to sort on. (Just to make sure the
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-- following won't confuse you, DISTINCT and ORDER BY can be used separately.)
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SELECT DISTINCT city
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FROM weather
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ORDER BY city;
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FROM weather
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ORDER BY city;
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-----------------------------
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-- Retrieving data into other classes:
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-- a SELECT ... INTO statement can be used to retrieve data into
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-- another class.
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-----------------------------
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SELECT * INTO TABLE mytemp
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FROM weather
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WHERE city = 'San Francisco'
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and prcp > 0.0;
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SELECT * from mytemp;
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-----------------------------
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-- Aggregates
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-----------------------------
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SELECT max(temp_lo)
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FROM weather;
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-- Aggregate with GROUP BY
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SELECT city, max(temp_lo)
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FROM weather
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GROUP BY city;
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-----------------------------
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-- Joining tables:
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-- Joins Between Tables:
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-- queries can access multiple tables at once or access the same table
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-- in such a way that multiple instances of the table are being processed
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-- at the same time.
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-----------------------------
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-- suppose we want to find all the records that are in the temperature range
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-- of other records. W1 and W2 are aliases for weather.
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-- The following joins the weather table and the cities table.
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SELECT *
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FROM weather, cities
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WHERE city = name;
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-- This prevents a duplicate city name column:
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SELECT city, temp_lo, temp_hi, prcp, date, location
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FROM weather, cities
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WHERE city = name;
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-- since the column names are all different, we don't have to specify the
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-- table name. If you want to be clear, you can do the following. They give
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-- identical results, of course.
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SELECT weather.city, weather.temp_lo, weather.temp_hi, weather.prcp, weather.date, cities.location
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FROM weather, cities
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WHERE cities.name = weather.city;
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-- JOIN syntax
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SELECT *
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FROM weather JOIN cities ON (weather.city = cities.name);
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-- Outer join
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SELECT *
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FROM weather LEFT OUTER JOIN cities ON (weather.city = cities.name);
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-- Suppose we want to find all the records that are in the temperature range
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-- of other records. W1 and W2 are aliases for weather.
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SELECT W1.city, W1.temp_lo, W1.temp_hi,
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W2.city, W2.temp_lo, W2.temp_hi
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@ -129,60 +136,69 @@ FROM weather W1, weather W2
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WHERE W1.temp_lo < W2.temp_lo
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and W1.temp_hi > W2.temp_hi;
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-- let's join two tables. The following joins the weather table
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-- and the cities table.
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SELECT city, location, prcp, date
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FROM weather, cities
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WHERE name = city;
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-- since the column names are all different, we don't have to specify the
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-- table name. If you want to be clear, you can do the following. They give
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-- identical results, of course.
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SELECT w.city, c.location, w.prcp, w.date
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FROM weather w, cities c
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WHERE c.name = w.city;
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-----------------------------
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-- Updating data:
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-- an UPDATE statement is used for updating data.
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-- Aggregate Functions
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-----------------------------
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-- suppose you discover the temperature readings are all off by 2 degrees as
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SELECT max(temp_lo)
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FROM weather;
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SELECT city FROM weather
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WHERE temp_lo = (SELECT max(temp_lo) FROM weather);
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-- Aggregate with GROUP BY
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SELECT city, max(temp_lo)
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FROM weather
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GROUP BY city;
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-- ... and HAVING
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SELECT city, max(temp_lo)
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FROM weather
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GROUP BY city
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HAVING max(temp_lo) < 40;
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-----------------------------
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-- Updates:
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-- An UPDATE statement is used for updating data.
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-----------------------------
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-- Suppose you discover the temperature readings are all off by 2 degrees as
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-- of Nov 28, you may update the data as follow:
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UPDATE weather
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SET temp_hi = temp_hi - 2, temp_lo = temp_lo - 2
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WHERE date > '11/28/1994';
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SET temp_hi = temp_hi - 2, temp_lo = temp_lo - 2
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WHERE date > '1994-11-28';
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SELECT * from weather;
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SELECT * FROM weather;
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-----------------------------
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-- Deleting data:
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-- a DELETE statement is used for deleting rows from a table.
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-- Deletions:
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-- A DELETE statement is used for deleting rows from a table.
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-----------------------------
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-- suppose you are no longer interested in the weather of Hayward, you can
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-- do the following to delete those rows from the table
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-- Suppose you are no longer interested in the weather of Hayward, then you can
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-- do the following to delete those rows from the table.
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DELETE FROM weather WHERE city = 'Hayward';
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SELECT * from weather;
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SELECT * FROM weather;
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-- you can also delete all the rows in a table by doing the following. (This
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-- You can also delete all the rows in a table by doing the following. (This
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-- is different from DROP TABLE which removes the table in addition to the
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-- removing the rows.)
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DELETE FROM weather;
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SELECT * from weather;
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SELECT * FROM weather;
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-----------------------------
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-- Removing the tables:
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-- DROP TABLE is used to remove tables. After you have done this, you
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-- DROP TABLE is used to remove tables. After you have done this, you
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-- can no longer use those tables.
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-----------------------------
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DROP TABLE weather, cities, mytemp;
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DROP TABLE weather, cities;
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