Python MySQLdb: connection.close() VS. cursor.close()

Question

If I use MySQLdb to connect to MySQL-Server through Python. I create a connection and a cursor like this:

connection = MySQLdb.connect(...)
cursor = connection.cursor()
# process

When the MySQL-processing is done one should close the connection. Now I was wondering: Is it sufficient to close the connection by doing:

connection.close()

or do I have to close the cursor first and then the connection? Like this:

cursor.close()
connection.close()

Answer 1

I will re-iterate the best practice at everyone who comes across the sql connection using MySQLdb or any other package to connect python2/3 needs to know this

(Following mock run assumes that you have a table named tablename in your sql database. It has got 4 columns/fields with names field1,field2,field3,field4). If your connection is local (same machine) then it is 127.0.0.1 also known as "localhost".

The process is to be simple 7 steps

1. Create connection
2. Create cursor
3. Create Query string
4. Execute the query
5. Commit to the query
6. Close the cursor
7. Close the connection

Here is a simple step by stem mock run

mydb = MySQLdb.connect(host=host, user=user, passwd=passwd, db=database, charset="utf8")
cursor = mydb.cursor()
query = "INSERT INTO tablename (text_for_field1, text_for_field2, text_for_field3, text_for_field4) VALUES (%s, %s, %s, %s)"
cursor.execute(query, (field1, field2, field3, field4))
mydb.commit()
cursor.close()
mydb.close()

Connection and cursor are different. connection is at the SQL level while cursor can be considered as a data element. You can have multiple cursors on the same data within single connection. It is an unusual occurrence to have multiple connections to same data from the same computer.

More has been described here "The cursor paradigm is not specific to Python but are a frequent data structure in databases themselves.

Depending on the underlying implementation it may be possible to generate several cursors sharing the same connection to a database. Closing the cursor should free resources associated to the query, including any results never fetched from the DB (or fetched but not used) but would not eliminate the connection to the database itself so you would be able to get a new cursor on the same database without the need to authenticate again."