For a simple select query like select column_name from table_name on a very large table, is it possible to have the output being provided as the scan of the table progresses?
If I abort the command after sometime, I expect to get output from the select at least thus far.
Think cat, which I believe won't wait till it completes the full read of the file.
Does MySQL or other RDBMS systems support this?
PostgreSQL always streams the result to the client, and usually it is the client library that collects the whole result set before returning it to the user.
The C API libpq has functionality that supports this. The main disadvantage with this approach is that you could get a run time error after you already have received a some rows, so that's a case you'd have to handle.
The traditional way to receive a query result in parts is to use a cursor and fetch results from it. This is a technique supported by all client APIs.
Cursors are probably what you are looking for, and they are supported by all RDBMS I know in some fashion.
