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
Replication should be used when which of the following exist?

All of these
The application's data can be somewhat out-of-date.
When transmission speeds and capacity in a network prohibit frequent refreshing of large tables.
When using many nodes with different operating systems and DBMSs and database designs.

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Distributed Databases
A distributed database is which of the following?

A single logical database that is spread to multiple locations and is interconnected by a network
A loose collection of file that is spread to multiple locations and is interconnected by a network
A single logical database that is limited to one location.
A loose collection of file that is limited to one location.

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