mirror of
https://github.com/postgres/postgres.git
synced 2026-06-08 00:28:59 -04:00
Bruce Momjian
147aa84c1a
saw a fix offered up. Since I'm gearing up to use Postgres and Python soon, I figured I'd have a hand at trying to get this sucker addressed. Apologies if this has already been plugged. I looked in the archives and never saw a response. At any rate, I must admit I don't think I fully understand the implications of some of the changes I made even though they appear to be straight forward. We all know the devil is in the details. Anyone more knowledgeable is requested to review my changes. :( I also updated the advanced.py script in a somewhat nonsensical fashion to make use of an int8 field in an effort to test this change. It seems to run okay, however, this is by no means an all exhaustive test. So, it's possible that a bumpy road may lay ahead for some. On the other hand...overflows (hopefully) previously lurked (long -> int conversion). Greg Copeland
199 lines
6.7 KiB
Python
Executable File
199 lines
6.7 KiB
Python
Executable File
#! /usr/bin/env 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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__________________________________________________________________
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MODULE ADVANCED.PY : ADVANCED POSTGRES SQL COMMANDS TUTORIAL
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This module is designed for being imported from python prompt
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In order to run the samples included here, first create a connection
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using : cnx = advanced.DB(...)
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The "..." should be replaced with whatever arguments you need to open an
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existing database. Usually all you need is the name of the database and,
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in fact, if it is the same as your login name, you can leave it empty.
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then start the demo with: advanced.demo(cnx)
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__________________________________________________________________
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"""
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from pg import DB
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import sys
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# waits for a key
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def wait_key():
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print "Press <enter>"
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sys.stdin.read(1)
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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 varchar(2)"
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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 varchar(2)) 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("INSERT INTO cities VALUES ('San Francisco', 7.24E+5, 63)")
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pgcnx.query("INSERT INTO cities VALUES ('Las Vegas', 2.583E+5, 2174)")
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pgcnx.query("INSERT INTO cities VALUES ('Mariposa', 1200, 1953)")
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pgcnx.query("INSERT INTO capitals VALUES ('Sacramento',3.694E+5,30,'CA')")
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pgcnx.query("INSERT INTO capitals VALUES ('Madison', 1.913E+5, 845, 'WI')")
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print
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print "SELECT * FROM cities"
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print pgcnx.query("SELECT * FROM cities")
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print "SELECT * FROM capitals"
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print pgcnx.query("SELECT * FROM capitals")
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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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print pgcnx.query("""SELECT name, altitude
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FROM cities
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WHERE altitude > 500""")
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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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print 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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# 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 " pay_by_extra_quarter int8[],"
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print " schedule text[][]"
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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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pay_by_extra_quarter int8[],
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schedule text[][])""")
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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 " '{9223372036854775800,9223372036854775800,9223372036854775800}',"
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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 " '{9223372036854775807,9223372036854775807,9223372036854775807}',"
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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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'{9223372036854775800,9223372036854775800,9223372036854775800}',
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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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'{9223372036854775807,9223372036854775807,9223372036854775807}',
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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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print 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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print
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print pgcnx.query("""SELECT name FROM sal_emp WHERE
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sal_emp.pay_by_extra_quarter[1] <> sal_emp.pay_by_extra_quarter[2]""")
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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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print pgcnx.query("SELECT sal_emp.pay_by_quarter[3] FROM sal_emp")
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print
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print "-- retrieve third quarter extra pay of all employees"
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print
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print "SELECT sal_emp.pay_by_extra_quarter[3] FROM sal_emp"
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print pgcnx.query("SELECT sal_emp.pay_by_extra_quarter[3] FROM sal_emp")
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print
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print "-- retrieve first two quarters of extra quarter pay of all employees"
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print
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print "SELECT sal_emp.pay_by_extra_quarter[1:2] FROM sal_emp"
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print
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print pgcnx.query("SELECT sal_emp.pay_by_extra_quarter[1:2] FROM sal_emp")
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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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print 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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# 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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array_demo(pgcnx)
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demo_cleanup(pgcnx)
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