What does executeQuery() return when called on a Statement?

What does executeQuery() return when called on a Statement?

• A. Nothing (void)
• B. A single row
• C. A ResultSet
• D. An integer update count

Answer: (C)

The main idea is that executeQuery is the JDBC method you use for SELECT statements, and it returns a ResultSet that represents the tabular data produced by the query. It’s not void, it’s not a single row, and it’s not an update count—the update count is what you get from executeUpdate for INSERT/UPDATE/DELETE. With the ResultSet you can iterate over all returned rows (using next()) and read each column with the appropriate getter methods. If the query yields no rows, the ResultSet is simply empty, but still valid. If you ever need to run a statement that might return either a ResultSet or an update count, you’d use execute, which returns a boolean indicating whether the first result is a ResultSet.

The main idea is that executeQuery is the JDBC method you use for SELECT statements, and it returns a ResultSet that represents the tabular data produced by the query. It’s not void, it’s not a single row, and it’s not an update count—the update count is what you get from executeUpdate for INSERT/UPDATE/DELETE. With the ResultSet you can iterate over all returned rows (using next()) and read each column with the appropriate getter methods. If the query yields no rows, the ResultSet is simply empty, but still valid. If you ever need to run a statement that might return either a ResultSet or an update count, you’d use execute, which returns a boolean indicating whether the first result is a ResultSet.