Subject get values for a certain timestamp
Author Josef Gschwendtner
Dear Firebird users,

does anybody have an idea how to solve the following problem in a clever

Our Situation:
We have a database with to tables (amongst others).
In table1 (MDP) are several thousand "machine-datapoints" (e.g
machine-speed or temperature)
For each of these datapoints we get data (values) (e.g. 5 m/s) which is
stored in table2 (MD).

Some datapoints are sending a value each second, some only once a day.
Therefore table MD has many million records. Each record has a foreign
key MDP, the value and the timestamp when the value has been measured.
On the timestamp-field in MD is an ascending index.

Our problem:
We need to view the (active) values/states of all datapoints at a
certain time, which is given by the user.

Therefore the challenge is, to find out (as fast as possible) the last
stored value/state of each datapoint before the given timestamp.

Thank you for sharing your knowledge.
Josef Gschwendtner