[Newbie] Strange output from list

[Gilles Ganault]

Hello

I'm getting some unwanted result when SELECTing data from an SQLite
database:

======
sql = 'SELECT id FROM master'
rows=list(curso r.execute(sql))
for id in rows:
sql = 'SELECT COUNT(code) FROM companies WHERE code="%s"' % id[0]
result = list(cursor.exe cute(sql))
print "Code=%s, number=%s" % (id[0],result[0])
======
Code=0111Z, number=(47,)
======

I expected to see "number=47" . Why does Python return "(47,)"?

Thank you.

[Steve Holden]

John Machin wrote:

On Nov 11, 10:47 pm, Steve Holden <st...@holdenwe b.comwrote:

>Chris Rebert wrote:

>>On Tue, Nov 11, 2008 at 12:56 AM, Gilles Ganault <nos...@nospam. comwrote:
On Mon, 10 Nov 2008 20:02:39 -0600, Andrew <alif...@gmail. comwrote:
sql = 'SELECT id FROM master'
rows=list(c ursor.execute(s ql))
for id in rows:
sql = 'SELECT COUNT(code) FROM companies WHERE code="%s"' % id[0]
result = list(cursor.exe cute(sql))
print "Code=%s, number=%s" % (id[0],result[0][0])
Using liberal "term rewriting", consider the following rough
equivalenci es in the code:
id[0] <==rows[INDEX_HERE][0] <==list(cursor. execute(sql))[INDEX_HERE][0]
result[0][0] <==list(cursor. execute(sql))[0][0]
Note that in both cases, the list is sliced twice; the for-loop just
conceals the `[INDEX_HERE]` implicit slicing that is caused by
iterating over the list.

You might also want to consider saving some time by using a SQL solution
(assuming SQLite supports it, which it should) (untested):

cursor.execute ("""
SELECT master.id, count(companies .code)
FROM master JOIN companies ON master.id = companies.code
GROUP BY companies.code" "")

Shouldn't it be GROUP BY master.id? I would have thought that SQL
would be sad about a non-aggregate (master.id) that's in the SELECT
list but not also in the GROUP BY list.

Well, I did say "untested". But in SQL Server, for example, any field
argument to COUNT() must be an aggregated column. So it may depend on
the SQL implementation. I should really have said

GROUP BY master.id, companies.code

which is the kind of stupidity SQL's brainless implementations force one
to resort to.

>for id, count in cursor.fetchall ():
print "Code=%s, number=%s" % (id, count)

I'd like to think it makes the Python a bit more readable too ...

Agreed. result[0][0] is an abomination.

Though one I am sure we have all used at times. The original code wasn't
too bad for a beginner.

regards
Steve
--
Steve Holden [phone] [phone]
Holden Web LLC http://www.holdenweb.com/

[Rob Williscroft]

Steve Holden wrote in news:mailman.38 04.1226412496.3 487.python-
li**@python.org in comp.lang.pytho n:

>Shouldn't it be GROUP BY master.id? I would have thought that SQL
would be sad about a non-aggregate (master.id) that's in the SELECT
list but not also in the GROUP BY list.

Well, I did say "untested". But in SQL Server, for example, any field
argument to COUNT() must be an aggregated column. So it may depend on
the SQL implementation. I should really have said

You must mean an "SQL Server" other than the Microsofts one, as:

select count( aid ) as "count"
from table_1
group by aid

count
-----------
8
8
8
8
8
8
8
8

(8 row(s) affected)

and:

select count( aid ) as "count"
from table_1

count
-----------
64

(1 row(s) affected)

Like it should.

Rob.
--
http://www.victim-prime.dsl.pipex.com/

[Steve Holden]

Rob Williscroft wrote:

Steve Holden wrote in news:mailman.38 04.1226412496.3 487.python-
li**@python.org in comp.lang.pytho n:

>>Shouldn't it be GROUP BY master.id? I would have thought that SQL
would be sad about a non-aggregate (master.id) that's in the SELECT
list but not also in the GROUP BY list.

Well, I did say "untested". But in SQL Server, for example, any field
argument to COUNT() must be an aggregated column. So it may depend on
the SQL implementation. I should really have said

You must mean an "SQL Server" other than the Microsofts one, as:

select count( aid ) as "count"
from table_1
group by aid

count
-----------
8
8
8
8
8
8
8
8

(8 row(s) affected)

and:

select count( aid ) as "count"
from table_1

count
-----------
64

(1 row(s) affected)

Like it should.

Hmm, strange. I must be thinking of some other SQL Server then. Or, more
likely, some other error situation.

regards
Steve
--
Steve Holden [phone] [phone]
Holden Web LLC http://www.holdenweb.com/