Handle Indexes in JavaDB Using JDBC Program

Indexes in a table are pointers to the data, these speed up the data retrieval from a table. If we use indexes, the INSERT and UPDATE statements get executed in a slower phase. Whereas SELECT and WHERE get executed with in lesser time.

Creating an index

CTREATE INDEX index_name on table_name (column_name);

Displaying the Indexes

SHOW INDEXES FROM table_name;

Dropping an index

DROP INDEX index_name;

Following JDBC program creates a table with name Emp in JavaDB. creates an index on it, displays the list of indexes and, deletes the created index.

Example

import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.SQLException;
import java.sql.Statement;
public class IndexesExample {
   public static void main(String args[]) throws Exception {
      //Registering the driver
      Class.forName("org.apache.derby.jdbc.EmbeddedDriver");
      //Getting the Connection object
      String URL = "jdbc:derby:MYDATABASE;create=true";
      Connection conn = DriverManager.getConnection(URL);
      //Creating the Statement object
      Statement stmt = conn.createStatement();
      //Creating the Emp table
      String createQuery = "CREATE TABLE Emp( "
         + "Id INT NOT NULL GENERATED ALWAYS AS IDENTITY, "
         + "Name VARCHAR(255), "
         + "Salary INT NOT NULL, "
         + "Location VARCHAR(255), "
         + "Phone_Number BIGINT )";
      stmt.execute(createQuery);
      System.out.println("Table created");
      System.out.println(" ");
      //Creating an Index on the column Salary
      stmt.execute("CREATE INDEX example_index on Emp (Salary)");
      System.out.println("Index example_index inserted");
      System.out.println(" ");
      //listing all the indexes
      System.out.println("Listing all the columns with indexes");
      //Dropping indexes
      stmt.execute("Drop INDEX example_index ");
   }
}

Output

On executing, this generates the following result
Table created
Index example_index inserted
Listing all the columns with indexes>