Tim Goldenwrote:
> Frank Millman wrote:
>>
>> I want the final WHERE clause to show 'WHERE todate IS NULL'.
>
> Of course, I understand that. What I mean is that if a piece
> of SQL say:
>
> WHERE table.column IS ?
>
> then the only possible (meaningful) value ? can have is
> NULL (or None, in python-speak). In fact, the IS NULL is
> really a sort of unary operator-expression, not an operator
> with a value.
>
>>
>> As a workaround, I suppose I could scan the argument list, and if I find
>> a None, substitute the ? with NULL in the SQL statement itself.
>
> Well, the code I posted previously, although tedious taken to
> extremes, will do that. (I have seen and used code like that in a number
> of production systems).
>
Thanks, Tim, for the detailed explanation. I appreciate your taking the
time.
It was difficult for me to use the code that you posted, because under my
present setup I define my SQL statements externally, and the WHERE clause
has to conform to one or more rows of six columns -
Test (WHERE or AND or OR)
Left bracket (either present or blank)
Column name
Operator
Expression
Right bracket (either present or blank)
I therefore used the workaround that I mentioned above, and it seems to work
fine, for both pyodbc and psycopg2.
Once again, many thanks.
Frank
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