Daniel Miller wrote:
Jonathan Hayward http://JonathansCorner.com wrote:
Is there a way to specify an insert that says "Overwrite any previous
rows containing this row's primary key"?
In SQL that's two queries:
delete from users where user_id = ?
insert into users (user_id, ...) values (?, ...)
SQLAlchemy can do that quite succinctly:
def overwrite(id, ...):
users.delete(users.c.user_id==id)
users.insert().execute(user_id=id, ...)
Note: by definition, if it's a primary key then there will be at most
one row with a given key value. Therefore, there will be at most one
row affected by the delete statement.
~ Daniel
For a database that supports triggers, you can define a trigger before
insert that checks for an existing row and deletes it. The trigger
function could also just update the existing row with the new values
instead of deleting the row.. and then discard the insert.
Of course, it's a whole different topic for discussion on whether or not
you should program the application that way. :)
-Dennis
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