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Merge in D'Arcy Cain's python interface (PyGreSQL 2.0)
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Marc G. Fournier
214
src/interfaces/python/tutorial/advanced.py
Executable file
214
src/interfaces/python/tutorial/advanced.py
Executable file
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#! /usr/local/bin/python
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# advanced.py - demo of advanced features of PostGres. Some may not be ANSI.
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# inspired from the Postgres tutorial
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# adapted to Python 1995 by Pascal Andre
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print "__________________________________________________________________"
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print "MODULE ADVANCED.PY : ADVANCED POSTGRES SQL COMMANDS TUTORIAL"
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print
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print "This module is designed for being imported from python prompt"
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print
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print "In order to run the samples included here, first create a connection"
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print "using : cnx = advanced.connect(...)"
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print "then start the demo with: advanced.demo(cnx)"
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print "__________________________________________________________________"
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from pgtools import *
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from pgext import *
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# inheritance features
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def inherit_demo(pgcnx):
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print "-----------------------------"
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print "-- Inheritance:"
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print "-- a table can inherit from zero or more tables. A query"
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print "-- can reference either all rows of a table or all rows "
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print "-- of a table plus all of its descendants."
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print "-----------------------------"
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print
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print "-- For example, the capitals table inherits from cities table."
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print "-- (It inherits all data fields from cities.)"
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print
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print "CREATE TABLE cities ("
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print " name text,"
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print " population float8,"
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print " altitude int"
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print ")"
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print
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print "CREATE TABLE capitals ("
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print " state char2"
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print ") INHERITS (cities)"
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pgcnx.query("CREATE TABLE cities (" \
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"name text," \
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"population float8," \
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"altitude int)")
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pgcnx.query("CREATE TABLE capitals (" \
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"state char2) INHERITS (cities)")
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wait_key()
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print
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print "-- now, let's populate the tables"
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print
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print "INSERT INTO cities VALUES ('San Francisco', 7.24E+5, 63)"
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print "INSERT INTO cities VALUES ('Las Vegas', 2.583E+5, 2174)"
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print "INSERT INTO cities VALUES ('Mariposa', 1200, 1953)"
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print
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print "INSERT INTO capitals VALUES ('Sacramento', 3.694E+5, 30, 'CA')"
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print "INSERT INTO capitals VALUES ('Madison', 1.913E+5, 845, 'WI')"
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print
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pgcnx.query(
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"INSERT INTO cities VALUES ('San Francisco', 7.24E+5, 63)")
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pgcnx.query(
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"INSERT INTO cities VALUES ('Las Vegas', 2.583E+5, 2174)")
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pgcnx.query(
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"INSERT INTO cities VALUES ('Mariposa', 1200, 1953)")
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pgcnx.query("INSERT INTO capitals" \
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" VALUES ('Sacramento', 3.694E+5, 30, 'CA')")
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pgcnx.query("INSERT INTO capitals" \
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" VALUES ('Madison', 1.913E+5, 845, 'WI')")
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print
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print "SELECT * FROM cities"
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q = pgcnx.query("SELECT * FROM cities")
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display(q.listfields(), q.getresult())
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print "SELECT * FROM capitals"
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q = pgcnx.query("SELECT * FROM capitals")
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display(q.listfields(), q.getresult())
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print
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print "-- like before, a regular query references rows of the base"
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print "-- table only"
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print
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print "SELECT name, altitude"
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print "FROM cities"
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print "WHERE altitude > 500;"
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q = pgcnx.query("SELECT name, altitude " \
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"FROM cities " \
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"WHERE altitude > 500")
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display(q.listfields(), q.getresult())
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print
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print "-- on the other hand, you can find all cities, including "
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print "-- capitals, that are located at an altitude of 500 'ft "
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print "-- or higher by:"
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print
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print "SELECT c.name, c.altitude"
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print "FROM cities* c"
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print "WHERE c.altitude > 500"
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q = pgcnx.query("SELECT c.name, c.altitude " \
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"FROM cities* c " \
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"WHERE c.altitude > 500")
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display(q.listfields(), q.getresult())
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# time travel features
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def time_travel(pgcnx):
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print "-----------------------------"
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print "-- Time Travel:"
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print "-- this feature allows you to run historical queries. "
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print "-----------------------------"
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print
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print "-- first, let's make some changes to the cities table (suppose"
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print "-- Mariposa's population grows 10% this year)"
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print
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print "UPDATE cities"
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print "SET population = population * 1.1"
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print "WHERE name = 'Mariposa';"
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pgcnx.query("UPDATE cities " \
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"SET population = population * 1.1" \
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"WHERE name = 'Mariposa'")
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wait_key()
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print
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print "-- the default time is the current time ('now'):"
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print
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print "SELECT * FROM cities WHERE name = 'Mariposa';"
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q = pgcnx.query("SELECT * FROM cities WHERE name = 'Mariposa'")
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display(q.listfields(), q.getresult())
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print
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print "-- we can also retrieve the population of Mariposa ever has. "
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print "-- ('epoch' is the earliest time representable by the system)"
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print
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print "SELECT name, population"
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print "FROM cities['epoch', 'now'] -- can be abbreviated to cities[,]"
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print "WHERE name = 'Mariposa';"
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q = pgcnx.query("SELECT name, population "
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"FROM cities['epoch', 'now'] "
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"WHERE name = 'Mariposa'")
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display(q.listfields(), q.getresult())
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# arrays attributes
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def array_demo(pgcnx):
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print "----------------------"
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print "-- Arrays:"
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print "-- attributes can be arrays of base types or user-defined "
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print "-- types"
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print "----------------------"
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print
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print "CREATE TABLE sal_emp ("
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print " name text,"
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print " pay_by_quarter int4[],"
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print " schedule char16[][]"
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print ")"
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pgcnx.query("CREATE TABLE sal_emp (" \
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"name text," \
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"pay_by_quarter int4[]," \
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"schedule char16[][])")
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wait_key()
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print
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print "-- insert instances with array attributes. "
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print " Note the use of braces"
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print
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print "INSERT INTO sal_emp VALUES ("
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print " 'Bill',"
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print " '{10000,10000,10000,10000}',"
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print " '{{\"meeting\", \"lunch\"}, {}}')"
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print
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print "INSERT INTO sal_emp VALUES ("
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print " 'Carol',"
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print " '{20000,25000,25000,25000}',"
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print " '{{\"talk\", \"consult\"}, {\"meeting\"}}')"
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print
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pgcnx.query("INSERT INTO sal_emp VALUES (" \
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"'Bill', '{10000,10000,10000,10000}'," \
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"'{{\"meeting\", \"lunch\"}, {}}')")
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pgcnx.query("INSERT INTO sal_emp VALUES (" \
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"'Carol', '{20000,25000,25000,25000}'," \
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"'{{\"talk\", \"consult\"}, {\"meeting\"}}')")
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wait_key()
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print
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print "----------------------"
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print "-- queries on array attributes"
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print "----------------------"
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print
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print "SELECT name FROM sal_emp WHERE"
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print " sal_emp.pay_by_quarter[1] <> sal_emp.pay_by_quarter[2]"
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print
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q = pgcnx.query("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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display(q.listfields(), q.getresult())
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print
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print "-- retrieve third quarter pay of all employees"
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print
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print "SELECT sal_emp.pay_by_quarter[3] FROM sal_emp"
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print
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q = pgcnx.query("SELECT sal_emp.pay_by_quarter[3] FROM sal_emp")
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display(q.listfields(), q.getresult())
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print
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print "-- select subarrays"
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print
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print "SELECT sal_emp.schedule[1:2][1:1] FROM sal_emp WHERE "
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print " sal_emp.name = 'Bill'"
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q = pgcnx.query("SELECT sal_emp.schedule[1:2][1:1] FROM sal_emp WHERE " \
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"sal_emp.name = 'Bill'")
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display(q.listfields(), q.getresult())
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# base cleanup
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def demo_cleanup(pgcnx):
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print "-- clean up (you must remove the children first)"
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print "DROP TABLE sal_emp"
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print "DROP TABLE capitals"
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print "DROP TABLE cities;"
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pgcnx.query("DROP TABLE sal_emp")
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pgcnx.query("DROP TABLE capitals")
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pgcnx.query("DROP TABLE cities")
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# main demo function
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def demo(pgcnx):
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inherit_demo(pgcnx)
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time_travel(pgcnx)
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array_demo(pgcnx)
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demo_cleanup(pgcnx)
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