Distributed Databases
A semijoin is which of the following?

Only the joining attributes are sent from one site to another and then all of the rows are returned.
Only the joining attributes are sent from one site to another and then only the required rows are returned.
All of the attributes are sent from one site to another and then only the required rows are returned.
All of the attributes are sent from one site to another and then only the required rows are returned.

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Distributed Databases
Which of the following is true concerning a global transaction?

The required data are located in at least one nonlocal site and the distributed DBMS passes the request to only the local DBMS.
The required data are at one local site and the distributed DBMS routes requests as necessary.
The required data are at one local site and the distributed DBMS passes the request to only the local DBMS.
The required data are located in at least one nonlocal site and the distributed DBMS routes requests as necessary.

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