destructive "SELECT" query for SQL?
Dr. Hawkins
dochawk at gmail.com
Sun Oct 6 18:05:08 EDT 2013
On Sun, Oct 6, 2013 at 10:39 AM, Peter Haworth <pete at lcsql.com> wrote:
> Not sure I fully understand but you can use the literal NULL in a SELECT
> statement, eg SELECT col1,col2,NULL FROM.....
>
I create a record in a sqlite :memory:, and give it a tentative id (a
negative number). It is conceivable that a couple of these accumulate
before synchronizing with the remote/master db.
I insert this information into the master, which causes a serial number to
be assigned on the primary index.
As part of the same transaction, I have a select which pulls this id back.
I use a field not used for this type of data to store a unique identifier
for the running program and the temporary id, allowing me to map the
universal uniq id to the in-memory database.
After the SELECT that brings this back, I would like that field to be
emptied in the postgres database.
At the moment, on the readback, I just leave an in-memory marker so that it
will wipe the field next time there is a a contact with the remote db, but
it would be nice to get it from the same transaction.
The funky INSERT I was thinking about would happen as something like
INSERT INTO masterDb (myData,) VALUES ("abc123") RETURNING
(serialNumber, -7)
where -7 was my temporary tag.
The problem is that if I follow this with a SELECT, even if UNION
compatible, I don't seem to get the return value.
(again, for those joining late, the lag of the remote transaction is
presumed to be the "expensive" part of the transaction)
--
Dr. Richard E. Hawkins, Esq.
(702) 508-8462
More information about the use-livecode
mailing list