MySQLdb: execute query results...

Sheila King sheila at spamcop.net
Mon Sep 1 01:57:07 CEST 2003


I have searched for an answer to this question on the comp.lang.python
archives at Google Groups, and also looked through the (sparse) MySQLdb
documentation, and cannot confirm for a FACT what I think I know.

Looking for affirmation before I go "assuming" something and getting myself
into trouble somewhere along the line...

Here is what I *think* I know...let me know if I'm wrong, for crying out
loud!!!

If I do something like:

>>> db = MySQLdb.connect(passwd="mypass", host="localhost",
...     db="mydb", user="myusername")
>>> c = db.cursor()

and then later do:

>>> result = c.execute("""<some proper MySQL query here>""")

doesn't result always return the number of affected rows?

As a more concrete example:

I made the following table:

mysql> CREATE TABLE example(
    -> name VARCHAR(14),
    -> AGE INT,
    -> COUNTRY VARCHAR(15));
Query OK, 0 rows affected (0.03 sec)


And then in Python did the following INSERTS and UPDATE:

>>> c.execute("""INSERT INTO example (name, AGE, COUNTRY) VALUES ("sheila", 29, "US");""")
1L
>>> c.execute("""INSERT INTO example (name, AGE, COUNTRY) VALUES ("arthur", 23, "NL");""")
1L
>>> c.execute("""INSERT INTO example (name, AGE, COUNTRY) VALUES ("bob", 29, "US");""")
1L
>>> result = c.execute("""UPDATE example SET AGE=30 WHERE AGE=29;""")
>>> result
2L


Can I *RELY* on that "2L" result of the UPDATE statement under the cursor's
"execute" method representing the number of rows updated? Or am I assuming
too much?

Like I say, I looked through several sources, including my O'Reilly MySQL
book and cannot verify this for a fact from docs.

I did find this, however:
http://www.mysql.com/doc/en/UPDATE.html

"UPDATE returns the number of rows that were actually changed. In MySQL
Version 3.22 or later, the C API function mysql_info() returns the number
of rows that were matched and updated and the number of warnings that
occurred during the UPDATE. "

Which seems to corroborate, although they are not referring to the Python
DB-API specifically.

Thanks for any clarification on this matter,


-- 
Sheila King
http://www.thinkspot.net/sheila/
http://www.k12groups.org/




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