What is true about an equijoin?
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You can join a maximum of two tables through an equijoin.
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You can join a maximum of two columns through an equijoin.
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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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To join two tables through an equijoin, the columns in the join condition must be primary key and foreign key columns.
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You specify an equijoin condition in the SELECT or FROM clauses of a SELECT statement.
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.
An equijoin links tables using equality conditions on matching columns, typically primary-key/foreign-key pairs. When joining n tables that each have a single-column primary key, you generally need at least n-1 join conditions to connect every table into one chain — fewer than that and some tables would be left unjoined (producing an unwanted Cartesian product). The other options are wrong because equijoins aren't capped at two tables or two columns, the join columns don't strictly have to be PK/FK (any columns with matching values work), and join conditions belong in the WHERE clause (or ON clause), not SELECT/FROM.