Topic: n00b python db question (Read 486 times)
I'm all squared away now. It seems the MySQL bindings in python are a lot more primitive than PDO in PHP. I guess I've been spoiled.
This works around the issue:
Code:
cursor.execute("SELECT COALESCE(max(tstamp), 0) FROM ratedata");
I think this is what is confusing python -
It seems to be interpreting NULL as a result row even in the CLI client. With PDO driver in PHP it does not.
When I ask python to print the row the result is
which is different from NULL and I am guessing it is the driver that does that.
In cases where MySQL returns NULL is there a way in python to detect that opposed to it returning a result?
With SELECT max(foo) it looks like the row count will always be 1 whether or not the result is null (because no records exist) or has a value.
Code:
MariaDB [tstbtcart]> SELECT max(tstamp) AS tstamp FROM ratedata;
+--------+
| tstamp |
+--------+
| NULL |
+--------+
1 row in set (0.00 sec)
MariaDB [tstbtcart]>
+--------+
| tstamp |
+--------+
| NULL |
+--------+
1 row in set (0.00 sec)
MariaDB [tstbtcart]>
It seems to be interpreting NULL as a result row even in the CLI client. With PDO driver in PHP it does not.
When I ask python to print the row the result is
Code:
(None,)
which is different from NULL and I am guessing it is the driver that does that.
In cases where MySQL returns NULL is there a way in python to detect that opposed to it returning a result?
With SELECT max(foo) it looks like the row count will always be 1 whether or not the result is null (because no records exist) or has a value.
Code:
cursor.execute("SELECT max(tstamp) AS tstamp FROM ratedata");
rows = cursor.fetchall()
if rows:
print "There were rows"
else:
print "There were no rows"
rows = cursor.fetchall()
if rows:
print "There were rows"
else:
print "There were no rows"
It seems python counts the result "none" as a row. So even if the database is empty and there is no max(tstamp) for it to select, it still seems to think there is a row.
This is different from the PDO behaviour in PHP that I am use to.
How, in python, do you determine the result of a query is an empty set?
I must have looked at least 20 different tutorials online and every damn one of them uses examples where there are results to the query.
Thanks for the solution
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