Question

I have a school project for a Python script which runs an SQL query and spits out results to a file… I have this so far and wanted some feedback on if this looks right or if I am way off (I’m using adodbapi). Thanks much!

import adodbapi

# Connect to the SQL DB

conn = adodbapi.connect("Provider=SQLDB;SERVER= x.x.x.x ;User Id=user;Password=pass;DATABASE=db database;")
curs = conn.cursor()

# Execute SQL query test_file.sql"

query = 'test_file'
curs.execute("SELECT test_file")
rows = curs.fetchall()
for row in rows:
    print test_file | test_file.txt


conn.close()

Answer 1

1. # Execute SQL query test_file.sql" You are not executing an SQL query from a file. You are executing the SQL query "SELECT test_file".
2. "SELECT test_file" is not valid SQL syntax for the SELECT query. See this tutorial on the SELECT statement.
3. rows = curs.fetchall(); for row in rows: ... is not a nice way of iterating through all the results of a query.
   • If your query returns large number of rows, say a million rows, then all one million rows will have to be transferred from the database to your python program before the loop can start. This could be very slow if the database server is on a remote machine.
   • Your program will have to allocate memory for the entire data set before work begins. This could be hundreds of megabytes.

The more Pythonic way of doing this is to avoid loading the entire data set into memory unless you have to. Using sqlite3 I would write:

results = curs.execute("SELECT * FROM table_name")
for row in results:
    print (row)

This way only one row is loaded at a time.

1. print test_file | test_file.txt: the print statement does not support the pipe operator for writing to a file. (Python is not a Linux shell!) See Python File I/O.
   Additionally, even if this syntax was correct, you have failed to put the file name in 'quote marks'. Without quotes, Python will interpret test_file.txt as the property txt of a variable called test_file. This will get you a NameError because there is no variable called test_file, or possibly an AttributeError.

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If you want to test your code without having to connecting to a network database, then use the sqlite3 module. This is a built-in library of Python, implementing a database similar to adodbapi.

import sqlite3
db_conn = sqlite3.connect(":memory:") # connect to temporary database
db_conn.execute("CREATE TABLE colours ( Name TEXT, Red INT, Green INT, Blue INT )")
db_conn.execute("INSERT INTO colours VALUES (?,?,?,?)", ('gray', 128, 128, 128))
db_conn.execute("INSERT INTO colours VALUES (?,?,?,?)", ('blue', 0, 0, 255))
results = db_conn.execute("SELECT * FROM colours")
for row in results:
    print (row)

In future please try running your code, or at least testing that individual lines do what you expect. Trying print test_file | test_file.txt in an interpreter would have given you a TypeError: unsupported operand type(s) for |: 'str' and 'str'.