--
-- Copyright (c) 1994, Andrew Yu, University of California
--
--- $Id: basics.source,v 1.1.1.1 1996/07/09 06:22:34 scrappy Exp $
+-- $PostgreSQL: pgsql/src/tutorial/basics.source,v 1.5 2003/11/29 22:41:33 pgsql Exp $
--
---------------------------------------------------------------------------
-----------------------------
--- Creating a table:
--- a CREATE TABLE is used to create base tables. POSTGRES SQL has
--- its own set of built-in types. (Note that keywords are case-
--- insensitive but identifiers are case-sensitive.)
+-- Creating a New Table:
+-- A CREATE TABLE is used to create base tables. PostgreSQL has
+-- its own set of built-in types. (Note that SQL is case-
+-- insensitive.)
-----------------------------
CREATE TABLE weather (
city varchar(80),
temp_lo int, -- low temperature
temp_hi int, -- high temperature
- prcp float8, -- precipitation
+ prcp real, -- precipitation
date date
-)
+);
CREATE TABLE cities (
name varchar(80),
location point
);
+
-----------------------------
--- Inserting data:
--- an INSERT statement is used to insert a new row into a table. There
+-- Populating a Table With Rows:
+-- An INSERT statement is used to insert a new row into a table. There
-- are several ways you can specify what columns the data should go to.
-----------------------------
--- 1. the simplest case is when the list of value correspond to the order of
+-- 1. The simplest case is when the list of value correspond to the order of
-- the columns specified in CREATE TABLE.
INSERT INTO weather
- VALUES ('San Francisco', 46, 50, 0.25, '11/27/1994')
+ VALUES ('San Francisco', 46, 50, 0.25, '1994-11-27');
INSERT INTO cities
- VALUES ('San Francisco', '(-194.0, 53.0)');
+ VALUES ('San Francisco', '(-194.0, 53.0)');
--- 2. you can also specify what column the values correspond to. (The columns
--- can be specified in any order. You may also omit any number of columns.
--- eg. unknown precipitation below)
+-- 2. You can also specify what column the values correspond to. (The columns
+-- can be specified in any order. You may also omit any number of columns,
+-- e.g., unknown precipitation below.
INSERT INTO weather (city, temp_lo, temp_hi, prcp, date)
- VALUES ('San Francisco', 43, 57, 0.0, '11/29/1994')
+ VALUES ('San Francisco', 43, 57, 0.0, '1994-11-29');
INSERT INTO weather (date, city, temp_hi, temp_lo)
- VALUES ('11/29/1994', 'Hayward', 54, 37);
+ VALUES ('1994-11-29', 'Hayward', 54, 37);
-----------------------------
--- Retrieving data:
--- a SELECT statement is used for retrieving data. The basic syntax is
--- SELECT columns FROM tables WHERE predicates
+-- Querying a Table:
+-- A SELECT statement is used for retrieving data. The basic syntax is
+-- SELECT columns FROM tables WHERE predicates.
-----------------------------
--- a simple one would be
+-- A simple one would be:
SELECT * FROM weather;
--- you may also specify expressions in the target list (the 'AS column'
--- specifies the column name of the result. It is optional.)
+-- You may also specify expressions in the target list. (The 'AS column'
+-- specifies the column name of the result. It is optional.)
SELECT city, (temp_hi+temp_lo)/2 AS temp_avg, date FROM weather;
--- if you want to retrieve rows that satisfy certain condition (ie. a
--- restriction), specify the condition in WHERE. The following retrieves
+-- If you want to retrieve rows that satisfy certain condition (i.e., a
+-- restriction), specify the condition in WHERE. The following retrieves
-- the weather of San Francisco on rainy days.
SELECT *
-FROM weather
-WHERE city = 'San Francisco'
- and prcp > 0.0;
+ FROM weather
+ WHERE city = 'San Francisco'
+ AND prcp > 0.0;
--- here is a more complicated one. Duplicates are removed when DISTINCT is
--- specified. ORDER BY specifies the column to sort on. (Just to make sure the
+-- Here is a more complicated one. Duplicates are removed when DISTINCT is
+-- specified. ORDER BY specifies the column to sort on. (Just to make sure the
-- following won't confuse you, DISTINCT and ORDER BY can be used separately.)
SELECT DISTINCT city
-FROM weather
-ORDER BY city;
+ FROM weather
+ ORDER BY city;
+
-----------------------------
--- Retrieving data into other classes:
--- a SELECT ... INTO statement can be used to retrieve data into
--- another class.
+-- Joins Between Tables:
+-- queries can access multiple tables at once or access the same table
+-- in such a way that multiple instances of the table are being processed
+-- at the same time.
-----------------------------
-SELECT * INTO TABLE temp
-FROM weather
-WHERE city = 'San Francisco'
- and prcp > 0.0;
+-- The following joins the weather table and the cities table.
-SELECT * from temp;
+SELECT *
+ FROM weather, cities
+ WHERE city = name;
------------------------------
--- Aggregates
------------------------------
+-- This prevents a duplicate city name column:
-SELECT max(temp_lo)
-FROM weather;
+SELECT city, temp_lo, temp_hi, prcp, date, location
+ FROM weather, cities
+ WHERE city = name;
--- Aggregate with GROUP BY
-SELECT city, max(temp_lo)
-FROM weather
-GROUP BY city;
+-- since the column names are all different, we don't have to specify the
+-- table name. If you want to be clear, you can do the following. They give
+-- identical results, of course.
------------------------------
--- Joining tables:
--- queries can access multiple tables at once or access the same table
--- in such a way that multiple instances of the table are being processed
--- at the same time.
------------------------------
+SELECT weather.city, weather.temp_lo, weather.temp_hi, weather.prcp, weather.date, cities.location
+ FROM weather, cities
+ WHERE cities.name = weather.city;
+
+-- JOIN syntax
--- suppose we want to find all the records that are in the temperature range
--- of other records. W1 and W2 are aliases for weather.
+SELECT *
+ FROM weather JOIN cities ON (weather.city = cities.name);
+
+-- Outer join
+
+SELECT *
+ FROM weather LEFT OUTER JOIN cities ON (weather.city = cities.name);
+
+-- Suppose we want to find all the records that are in the temperature range
+-- of other records. W1 and W2 are aliases for weather.
SELECT W1.city, W1.temp_lo, W1.temp_hi,
W2.city, W2.temp_lo, W2.temp_hi
WHERE W1.temp_lo < W2.temp_lo
and W1.temp_hi > W2.temp_hi;
--- let's join two tables. The following joins the weather table
--- and the cities table.
-SELECT city, location, prcp, date
-FROM weather, cities
-WHERE name = city;
+-----------------------------
+-- Aggregate Functions
+-----------------------------
--- since the column names are all different, we don't have to specify the
--- table name. If you want to be clear, you can do the following. They give
--- identical results, of course.
+SELECT max(temp_lo)
+ FROM weather;
+
+SELECT city FROM weather
+ WHERE temp_lo = (SELECT max(temp_lo) FROM weather);
+
+-- Aggregate with GROUP BY
+SELECT city, max(temp_lo)
+ FROM weather
+ GROUP BY city;
+
+-- ... and HAVING
+SELECT city, max(temp_lo)
+ FROM weather
+ GROUP BY city
+ HAVING max(temp_lo) < 40;
-SELECT w.city, c.location, w.prcp, w.date
-FROM weather w, cities c
-WHERE c.name = w.city;
-----------------------------
--- Updating data:
--- an UPDATE statement is used for updating data.
+-- Updates:
+-- An UPDATE statement is used for updating data.
-----------------------------
--- suppose you discover the temperature readings are all off by 2 degrees as
+-- Suppose you discover the temperature readings are all off by 2 degrees as
-- of Nov 28, you may update the data as follow:
UPDATE weather
- SET temp_hi = temp_hi - 2, temp_lo = temp_lo - 2
- WHERE date > '11/28/1994';
+ SET temp_hi = temp_hi - 2, temp_lo = temp_lo - 2
+ WHERE date > '1994-11-28';
-SELECT * from weather;
+SELECT * FROM weather;
-----------------------------
--- Deleting data:
--- a DELETE statement is used for deleting rows from a table.
+-- Deletions:
+-- A DELETE statement is used for deleting rows from a table.
-----------------------------
--- suppose you are no longer interested in the weather of Hayward, you can
--- do the following to delete those rows from the table
+-- Suppose you are no longer interested in the weather of Hayward, then you can
+-- do the following to delete those rows from the table.
DELETE FROM weather WHERE city = 'Hayward';
-SELECT * from weather;
+SELECT * FROM weather;
--- you can also delete all the rows in a table by doing the following. (This
+-- You can also delete all the rows in a table by doing the following. (This
-- is different from DROP TABLE which removes the table in addition to the
-- removing the rows.)
DELETE FROM weather;
-SELECT * from weather;
+SELECT * FROM weather;
+
-----------------------------
-- Removing the tables:
--- DROP TABLE is used to remove tables. After you have done this, you
+-- DROP TABLE is used to remove tables. After you have done this, you
-- can no longer use those tables.
-----------------------------
-DROP TABLE weather, cities, temp;
+DROP TABLE weather, cities;
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