Notification of SQL results off-date

DataBase is always treated as a passive source of data. The client executes queries and cares about the up to date of the received results.

I want to present a possible reverse of policy, when the client declares its interest of up to date results and the database informs the interested clients when the last sent result is off-date.

After executing a query and receiving table of results some changes can be made and affect the requested data in the DateBase. Imagine the DataBase service provides clients with specifying a special command to execute when a change is made in the results table. Doing so when an update is made in the DB, all important results which have to be kept up to date will be informed if are affected by the first.

A boolean formula can be presented in the place of a single change notification flag. When this formula is true the set command is executed and this way the service informed about the off-date data.