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+#! /usr/bin/env python
+# basics.py - basic SQL commands tutorial
+# inspired from the Postgres95 tutorial 
+# adapted to Python 1995 by Pascal ANDRE
+
+print """
+__________________________________________________________________
+MODULE BASICS.PY : BASIC POSTGRES SQL COMMANDS TUTORIAL
+    
+This module is designed for being imported from python prompt
+    
+In order to run the samples included here, first create a connection
+using :                        cnx = advanced.DB(...)
+  
+The "..." should be replaced with whatever arguments you need to open an
+existing database.  Usually all you need is the name of the database and,
+in fact, if it is the same as your login name, you can leave it empty.
+        
+then start the demo with:      basics.demo(cnx)
+__________________________________________________________________
+""" 
+
+from pg import DB
+import sys
+
+# waits for a key
+def wait_key():
+	print "Press <enter>"
+	sys.stdin.read(1)
+
+# table creation commands
+def create_table(pgcnx):
+	print "-----------------------------"
+	print "-- Creating a table:"
+	print "--  a CREATE TABLE is used to create base tables. POSTGRES"
+	print "--  SQL has its own set of built-in types. (Note that"
+	print "--  keywords are case-insensitive but identifiers are "
+	print "--  case-sensitive.)"
+	print "-----------------------------"
+	print
+	print "Sending query :"
+	print "CREATE TABLE weather ("
+        print "    city            varchar(80),"
+        print "    temp_lo         int,"
+        print "    temp_hi         int,"
+        print "    prcp            float8,"
+        print "    date            date"
+        print ")"
+        pgcnx.query("""CREATE TABLE weather (city varchar(80), temp_lo int,
+            temp_hi int, prcp float8, date date)""")
+	print
+	print "Sending query :"
+	print "CREATE TABLE cities ("
+	print "    name        varchar(80),"
+	print "    location    point"
+	print ")"
+	pgcnx.query("""CREATE TABLE cities (
+        name     varchar(80),
+        location point)""")
+
+# data insertion commands
+def insert_data(pgcnx):
+	print "-----------------------------"
+	print "-- Inserting data:"
+	print "--  an INSERT statement is used to insert a new row into"
+	print "--  a table. There are several ways you can specify what"
+	print "--  columns the data should go to."
+	print "-----------------------------"
+	print
+	print "-- 1. the simplest case is when the list of value correspond to"
+	print "--    the order of the columns specified in CREATE TABLE."
+	print
+	print "Sending query :"
+	print "INSERT INTO weather "
+	print "   VALUES ('San Francisco', 46, 50, 0.25, '11/27/1994')"
+	pgcnx.query("""INSERT INTO weather
+        VALUES ('San Francisco', 46, 50, 0.25, '11/27/1994')""")
+	print
+	print "Sending query :"
+	print "INSERT INTO cities "
+	print "   VALUES ('San Francisco', '(-194.0, 53.0)')"
+	pgcnx.query("""INSERT INTO cities
+        VALUES ('San Francisco', '(-194.0, 53.0)')""")
+	print
+	wait_key()
+	print "-- 2. you can also specify what column the values correspond "
+	print "     to. (The columns can be specified in any order. You may "
+	print "     also omit any number of columns. eg. unknown precipitation"
+	print "     below)"
+	print "Sending query :"
+	print "INSERT INTO weather (city, temp_lo, temp_hi, prcp, date)"
+	print "   VALUES ('San Francisco', 43, 57, 0.0, '11/29/1994')"
+	pgcnx.query("INSERT INTO weather (date, city, temp_hi, temp_lo)" \
+        "VALUES ('11/29/1994', 'Hayward', 54, 37)")
+
+# direct selection commands
+def select_data1(pgcnx):
+	print "-----------------------------"
+	print "-- Retrieving data:"
+	print "--  a SELECT statement is used for retrieving data. The "
+	print "--  basic syntax is:"
+	print "--      SELECT columns FROM tables WHERE predicates"
+	print "-----------------------------"
+	print
+	print "-- a simple one would be the query:"
+	print "SELECT * FROM weather"
+	print 
+	print "The result is :"
+	q = pgcnx.query("SELECT * FROM weather")
+	print q
+	print
+	print "-- you may also specify expressions in the target list (the "
+	print "-- 'AS column' specifies the column name of the result. It is "
+	print "-- optional.)"
+	print "The query :"
+	print "   SELECT city, (temp_hi+temp_lo)/2 AS temp_avg, date "
+	print "   FROM weather"
+	print "Gives :"
+	print pgcnx.query("""SELECT city, (temp_hi+temp_lo)/2
+        AS temp_avg, date FROM weather""")
+	print
+	print "-- if you want to retrieve rows that satisfy certain condition"
+	print "-- (ie. a restriction), specify the condition in WHERE. The "
+	print "-- following retrieves the weather of San Francisco on rainy "
+	print "-- days."
+	print "SELECT *"
+	print "FROM weather"
+	print "WHERE city = 'San Francisco' "
+	print "  and prcp > 0.0"
+	print pgcnx.query("""SELECT * FROM weather WHERE city = 'San Francisco'
+        AND prcp > 0.0""")
+	print
+	print "-- here is a more complicated one. Duplicates are removed when "
+	print "-- DISTINCT is specified. ORDER BY specifies the column to sort"
+	print "-- on. (Just to make sure the following won't confuse you, "
+	print "-- DISTINCT and ORDER BY can be used separately.)"
+	print "SELECT DISTINCT city"
+	print "FROM weather"
+	print "ORDER BY city;"
+	print pgcnx.query("SELECT DISTINCT city FROM weather ORDER BY city")
+
+# selection to a temporary table
+def select_data2(pgcnx):
+	print "-----------------------------"
+	print "-- Retrieving data into other classes:"
+	print "--  a SELECT ... INTO statement can be used to retrieve "
+	print "--  data into another class."
+	print "-----------------------------"
+	print 
+	print "The query :"
+	print "SELECT * INTO TABLE temptab "
+	print "FROM weather"
+	print "WHERE city = 'San Francisco' "
+	print "  and prcp > 0.0"
+	pgcnx.query("""SELECT * INTO TABLE temptab FROM weather
+        WHERE city = 'San Francisco' and prcp > 0.0""")
+	print "Fills the table temptab, that can be listed with :"
+	print "SELECT * from temptab"
+	print pgcnx.query("SELECT * from temptab")
+
+# aggregate creation commands
+def create_aggregate(pgcnx):
+	print "-----------------------------"
+	print "-- Aggregates"
+	print "-----------------------------"
+	print
+	print "Let's consider the query :"
+	print "SELECT max(temp_lo)"
+	print "FROM weather;"
+	print pgcnx.query("SELECT max(temp_lo) FROM weather")
+	print 
+	print "-- Aggregate with GROUP BY"
+	print "SELECT city, max(temp_lo)"
+	print "FROM weather "
+	print "GROUP BY city;"
+	print pgcnx.query( """SELECT city, max(temp_lo)
+        FROM weather GROUP BY city""")
+
+# table join commands
+def join_table(pgcnx):
+	print "-----------------------------"
+	print "-- Joining tables:"
+	print "--  queries can access multiple tables at once or access"
+	print "--  the same table in such a way that multiple instances"
+	print "--  of the table are being processed at the same time."
+	print "-----------------------------"
+	print
+	print "-- suppose we want to find all the records that are in the "
+	print "-- temperature range of other records. W1 and W2 are aliases "
+	print "--for weather."
+	print
+	print "SELECT W1.city, W1.temp_lo, W1.temp_hi, "
+	print "    W2.city, W2.temp_lo, W2.temp_hi"
+	print "FROM weather W1, weather W2"
+	print "WHERE W1.temp_lo < W2.temp_lo "
+	print "  and W1.temp_hi > W2.temp_hi"
+	print
+	print pgcnx.query("""SELECT W1.city, W1.temp_lo, W1.temp_hi,
+        W2.city, W2.temp_lo, W2.temp_hi FROM weather W1, weather W2
+        WHERE W1.temp_lo < W2.temp_lo and W1.temp_hi > W2.temp_hi""")
+	print
+	print "-- let's join two tables. The following joins the weather table"
+	print "-- and the cities table."
+	print
+	print "SELECT city, location, prcp, date"
+	print "FROM weather, cities"
+	print "WHERE name = city"
+	print
+	print pgcnx.query("""SELECT city, location, prcp, date FROM weather, cities
+        WHERE name = city""")
+	print
+	print "-- since the column names are all different, we don't have to "
+	print "-- specify the table name. If you want to be clear, you can do "
+	print "-- the following. They give identical results, of course."
+	print
+	print "SELECT w.city, c.location, w.prcp, w.date"
+	print "FROM weather w, cities c"
+	print "WHERE c.name = w.city;"
+	print
+	print pgcnx.query("""SELECT w.city, c.location, w.prcp, w.date
+        FROM weather w, cities c WHERE c.name = w.city""")
+
+# data updating commands
+def update_data(pgcnx):
+	print "-----------------------------"
+	print "-- Updating data:"
+	print "--  an UPDATE statement is used for updating data. "
+	print "-----------------------------"
+	print 
+	print "-- suppose you discover the temperature readings are all off by"
+	print "-- 2 degrees as of Nov 28, you may update the data as follow:"
+	print
+	print "UPDATE weather"
+	print "  SET temp_hi = temp_hi - 2,  temp_lo = temp_lo - 2"
+	print "  WHERE date > '11/28/1994'"
+	print
+	pgcnx.query("""UPDATE weather
+        SET temp_hi = temp_hi - 2,  temp_lo = temp_lo - 2
+        WHERE date > '11/28/1994'""")
+	print
+	print "SELECT * from weather"
+	print pgcnx.query("SELECT * from weather")
+
+# data deletion commands
+def delete_data(pgcnx):
+	print "-----------------------------"
+	print "-- Deleting data:"
+	print "--  a DELETE statement is used for deleting rows from a "
+	print "--  table."
+	print "-----------------------------"
+	print
+	print "-- suppose you are no longer interested in the weather of "
+	print "-- Hayward, you can do the following to delete those rows from"
+	print "-- the table"
+	print
+	print "DELETE FROM weather WHERE city = 'Hayward'"
+	pgcnx.query("DELETE FROM weather WHERE city = 'Hayward'")
+	print
+	print "SELECT * from weather"
+	print
+	print pgcnx.query("SELECT * from weather")
+	print
+	print "-- you can also delete all the rows in a table by doing the "
+	print "-- following. (This is different from DROP TABLE which removes "
+	print "-- the table in addition to the removing the rows.)"
+	print
+	print "DELETE FROM weather"
+	pgcnx.query("DELETE FROM weather")
+	print
+	print "SELECT * from weather"
+	print pgcnx.query("SELECT * from weather")
+
+# table removal commands
+def remove_table(pgcnx):
+	print "-----------------------------"
+	print "-- Removing the tables:"
+	print "--  DROP TABLE is used to remove tables. After you have"
+	print "--  done this, you can no longer use those tables."
+	print "-----------------------------"
+	print
+	print "DROP TABLE weather, cities, temptab"
+	pgcnx.query("DROP TABLE weather, cities, temptab")
+
+# main demo function
+def demo(pgcnx):
+	create_table(pgcnx)
+	wait_key()
+	insert_data(pgcnx)
+	wait_key()
+	select_data1(pgcnx)
+	select_data2(pgcnx)
+	create_aggregate(pgcnx)
+	join_table(pgcnx)
+	update_data(pgcnx)
+	delete_data(pgcnx)
+	remove_table(pgcnx)