Question

What will the following piece of Java code do? In few sentences, describe how this Java code [does | does not] change the state of the database.

public static void updateEvent (Connection conn, int eid, double v) throws Exception
{
int val = -1;
String query = "select * from ORDERS where EventID = ?";
PreparedStatement stmt = conn.prepareStatement (query);
stmt.setInt(1, eid);
ResultSet rs = stmt.executeQuery();
if(rs.next())
{
val = rs.getInt ("TicketPrice");
}
else
{
val = V;
}
}
2. Beyond what the above Java code does or doesn't do with the database, there is something that this Java code does wrong (or is missing). Explain why this Java code is written poorly. What happens if you use it in the loop? Base your answer on content of Chapter 10 and PowerPoint presentation slides-Java JDBC-Basic Usage-7 steps. Are all the steps properly implemented?

Answer 1

This Java code retrieves data from a database table but does not update the state of the database. It is missing the step to execute an UPDATE statement.

Step-by-step explanation:

This Java code is designed to update the state of a row in a database table called ORDERS. It takes three parameters: a Connection object, an integer eid, and a double v. The code first executes a SQL query to retrieve the TicketPrice from the ORDERS table where the EventID matches the provided eid. If a row is found, the TicketPrice value is stored in the variable val. If no row is found, the value of val is set to the provided double v. The code does not actually update the state of the database, only retrieves data from it and assigns values to variables.

This Java code is written poorly because it is missing the step of executing an UPDATE statement to modify the state of the database. In a loop, using this code would repeatedly retrieve data from the database without actually updating it. The missing step is the execution of an UPDATE statement with the appropriate query to modify the TicketPrice value for the specified EventID.