Pyodbc and Access with query parameter that contains a period - sql

Question

I recently found a bug with some Access SQL queries that I can't seem to track down. I have a fairly straightforward SQL query that I use to retrieve data from an access database that's "managed" in an older application (ie the data is already in the database and I have no real control over what's in there).
import pyodbc
MDB = '******.MDB'
DRV = '{Microsoft Access Driver (*.mdb)}'
PWD = ''
con = pyodbc.connect('DRIVER={};DBQ={};PWD={}'.format(DRV, MDB, PWD))
sql = ('SELECT Estim.PartNo, Estim.Descrip, Estim.CustCode, Estim.User_Text1, Estim.Revision, ' +
'Estim.Comments, Routing.PartNo AS RPartNo, Routing.StepNo, Routing.WorkCntr, Routing.VendCode, ' +
'Routing.Descrip AS StepDescrip, Routing.SetupTime, Routing.CycleTime, ' +
'Routing.WorkOrVend, ' +
'Materials.PartNo as MatPartNo, Materials.SubPartNo, Materials.Qty, ' +
'Materials.Unit, Materials.TotalQty, Materials.ItemNo, Materials.Vendor ' +
'FROM (( Estim ' +
'INNER JOIN Routing ON Estim.PartNo = Routing.PartNo ) ' +
'INNER JOIN Materials ON Estim.PartNo = Materials.PartNo )')
if 'PartNo' in kwargs:
key = kwargs['PartNo']
sql = sql + 'WHERE Estim.PartNo=?'
cursor = con.cursor().execute(sql, key)
# use this for debuging only
num = 0
for row in cursor.fetchall():
num += 1
return num
This works fine for all PartNo except when PartNo contains a decimal point. Curiously, when PartNo contains a decimal point AND a hyphen, I get the appropriate record(s).
kwargs['PartNo'] = "100.100-2" # returns 1 record
kwargs['PartNo'] = "200.100" # returns 0 records
Both PartNos exist when viewed in the other application, so I know there should be records returned for both queries.
My first thought was to ensure kwargs['PartNo'] is a string key = str(kwargs['PartNo']) with no change.
I also tried to places quotes around the 'PartNo' value with no success. key = '\'' + kwargs['PartNo'] + '\''
Finally, I tried to escape the . with no success (I realize this would break most queries, but I'm just trying to track down the issue with a single period) key = str(kwargs['partNo']).replace('.', '"."')
I know using query parameters should handle all the escaping for me, but at this point, I'm just trying to figure out what's going on. Any thoughts on this?

Answer 1

So the issue isn't with the query parameters - everything works as it should. The problem is with the SQL statement. I incorrectly assumed - and never checked - that there was a record in the Materials table that matched PartNo.
INNER JOIN Materials ON Estim.PartNo = Materials.PartNo
will only return a record if PartNo is found in both tables, which in this particular case it is not.
Changing it to
LEFT OUTER JOIN Materials ON Estim.PartNo = Materials.PartNo
produces the expected results. See this for info on JOINS. https://msdn.microsoft.com/en-us/library/bb243855(v=office.12).aspx
As for print (repr(key)) - flask handles the kwarg type upstream properly
api.add_resource(PartAPI, '/api/v1.0/part/<string:PartNo>'
so when I ran this in the browser, I got the "full length" strings. When run in the cmd line using python -c ....... I was not handling the argument type properly as Gord pointed out, so it was truncating the trailing zeros. I didn't think the flask portion was relevant, so I never added that in the original question.