-- if you are looking for an answer specific to hibernate, check @Mark's answer
Given the Employee example -assuming the number of employees can scale over time, it is better to use an approach to query the database for the exact data.
However, if you are considering something like Department (for example), where the chances of the data growing rapidly is less, it is useful to query all of them and have in memory - this way you don't have to reach to the external resource (database) every time, which could be costly.
So the general parameters are these,
- scaling of data
- criticality to bussiness
- volume of data
- frequency of usage
to put some sense, when the data is not going to scale frequently and the data is not mission critical and volume of data is manageable in memory on the application server and is used frequently - Bring it all and filter them programatically, if needed.
if otherwise get only specific data.
