As an example for my class on the usefulness of Common Table Expressions (CTEs), I created three examples with Python. They extend an exercise in Chapter 9 on subqueries from Learning SQL by Alan Beaulieu. All of the examples work with the sakila sample database.

These bullets describe the examples:

1. Uses local variables and a range for loop and if statement that uses the variables to evaluate and add an element to the derived table (or query result set) from MySQL.
2. Uses a CTE with substitution variables from the Python program, which eliminates the need to evaluate and add an element to the query result set because the query does that.
3. Uses a table to hold the variables necessary to evaluate and add the element to the query result set.

This is the first Python program:

# Import the library.
import sys
import …

Somebody asked me how to expand a prior example with the static variables so that it took arguments at the command line for the variables. This example uses Python 3 new features in the datetime package.

There’s a small trick converting the string arguments to date data types. Here’s a quick example that shows you how to convert the argument list into individual date data type variables:

#!/usr/bin/python3

# include standard modules
import sys
from datetime import datetime

# Capture argument list.
fullCmdArguments = sys.argv

# Assignable variables.
beginDate = ""
endDate = ""

# Assign argument list to variable.
argumentList = fullCmdArguments[1:]

# Enumerate through the argument list where beginDate precedes endDate as strings.
try:
  for i, s in enumerate(argumentList):
    if (i == …

While building my student image on Fedora 30, I installed the MySQL PHP Connector (php-mysqlndrp) but neglected to install the Python Connector. This adds the installation and basic test of the Python Connector to the original blog post.

You use the following command with a wildcard as a privileged user. The wildcard is necessary because you need to load two libraries to support Python 2.7 and 3.7, which are installed on Fedora 30. You also need to be the root user or a user that is found in the sudoer’s list:

yum install -y mysql-connector-python*

Display detailed console log →

Last metadata expiration check: 0:35:46 ago on Tue 20 Aug 2019 05:36:29 PM MDT.
Dependencies resolved. …