What is true about an equijoin?

technology databases

  1. You can join a maximum of two tables through an equijoin.

  2. You can join a maximum of two columns through an equijoin.

  3. You can join n tables (all having single column primary keys) in a SQL statement by specifying a minimum of n-1 join conditions.

  4. To join two tables through an equijoin, the columns in the join condition must be primary key and foreign key columns.

  5. You specify an equijoin condition in the SELECT or FROM clauses of a SELECT statement.

Show answer
Correct Option: C
Explanation:

To solve this question, the user needs to have knowledge of SQL and database concepts related to joining tables.

A. This option is incorrect because you can join any number of tables through an equijoin, not just a maximum of two.

B. This option is incorrect because you can join any number of columns through an equijoin, not just a maximum of two.

C. This option is correct. In a SQL statement, you can join n tables (all having single column primary keys) by specifying a minimum of n-1 join conditions.

D. This option is incorrect because while it is true that you can join two tables through an equijoin, the columns in the join condition do not have to be primary key and foreign key columns. They just need to have matching values.

E. This option is incorrect because you specify an equijoin condition in the WHERE clause of a SELECT statement.

Therefore, the correct answer is:

The Answer is: C. You can join n tables (all having single column primary keys) in a SQL statement by specifying a minimum of n-1 join conditions.

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