Path: csiph.com!fu-berlin.de!uni-berlin.de!not-for-mail
From: Michael Torrie <torriem@gmail.com>
Newsgroups: comp.lang.python
Subject: Re: Cannot step through asynchronous iterator manually
Date: Sat, 30 Jan 2016 15:05:09 -0700
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On 01/30/2016 02:57 PM, Michael Torrie wrote:
> SELECT count(some_id_field),field1,field2,field3 FROM wherever WHERE
> conditions
> 
> If the first column (or whatever you decide to alias it as) contains a
> count, and the rest of the information is still there.  If count is 1,
> then the row is what you want and you can do whatever you wish with it.
>  If not, throw your exception.

I'm not sure how SQLite handles it, or even what the SQL spec says, but
I know in MySQL you could do something like this:

SELECT count(id) as row_count,`tablename`.* FROM `tablename` WHERE condition

and get the same thing as SELECT * would have, with the addition of a
"row_count" field.  Note that because of the count() part, the query
will always only return 1 row. The fields will be NULL if the count was
zero or they will contain the fields from the last row the query found.
 In other words if there is more than one row that matches the query, it
will only give you data from the last match.

Now if Frank is hoping to do work on the first row and then throw an
exception if there's an additional row, then this of course won't work
for him.