In a semijoin, only the joining attribute is sent from one site to another, and then only the required rows are returned.

Answer: Option A

The statement is true. In a semijoin operation, only the joining attribute is sent from one site to another, and then only the required rows are returned, reducing the amount of data transmitted between distributed database nodes.

Option A: True
This option correctly affirms the statement provided in the question. In a semijoin operation, only the attributes needed for join conditions (i.e., the joining attribute) are sent from one site to another. Once the receiving site receives the joining attribute, it performs a local join operation using its own data and returns only the rows that satisfy the join condition. By transmitting only the necessary attribute and minimizing data transfer between nodes, the semijoin approach helps reduce network traffic and improve query performance in distributed database systems.

Option B: False
This option contradicts the statement provided in the question. The semijoin operation is specifically designed to minimize network traffic by sending only the joining attribute between distributed database nodes. By transmitting only the required attribute for join conditions, the semijoin approach can optimize query processing and reduce the impact of data transfer overhead on distributed database performance.

Therefore, in response to the question, the correct option is True (Option A).