On 13-9-2015 04:33, thirdshiftcoder@... [firebird-support] wrote:

> I read through and practiced with all types of read committed
> transactions with and without wait. I understand those scenarios as they
> apply to read write with, for i.e., update statements.
>
> I am trying to figure out besides snapshot, which is the default
> isolation in isql, how a select query would be useful when used in
> another isolation level.
>
> thanks for any examples.

Depending on the isolation level, you will only see changes committed
before your transaction started (eg snapshot), or any changes committed
at the time they are read (read committed).

This last feature might be useful if you are interested in timely
information, not necessarily fully consistent data. Eg for something
like a dashboard, having the latest information available can be more
important.

Also note that on other database systems, the transaction guarantees of
something like snapshot can be more expensive, so read committed is
usually "good enough" and people are more familiar with its behavior
(usually implicitly); having an equivalent in Firebird makes it easier.

Mark
--
Mark Rotteveel