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How to delete a column from an existing table in a database using JDBC API?
You can delete a column in a table using the ALTER TABLE command.
Syntax
ALTER TABLE table_name DROP COLUMN column_name;
Assume we have a table named Sales in the database with 7 columns namely id, CustomerName, DispatchDate, DeliveryTime, Price and, Location as shown below:
+----+-------------+--------------+--------------+--------------+-------+----------------+ | id | productname | CustomerName | DispatchDate | DeliveryTime | Price | Location | +----+-------------+--------------+--------------+--------------+-------+----------------+ | 1 | Key-Board | Raja | 2019-09-01 | 08:51:36 | 7000 | Hyderabad | | 2 | Earphones | Roja | 2019-05-01 | 05:54:28 | 2000 | Vishakhapatnam | | 3 | Mouse | Puja | 2019-03-01 | 04:26:38 | 3000 | Vijayawada | | 4 | Mobile | Vanaja | 2019-03-01 | 04:26:35 | 9000 | Chennai | | 5 | Headset | Jalaja | 2019-04-06 | 05:19:16 | 6000 | Delhi | +----+-------------+--------------+--------------+--------------+-------+----------------+
Following JDBC program establishes connection with MySQL database, and deletes the column named ID to from the Sales table.
import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.SQLException;
import java.sql.Statement;
public class DeletingColumn {
public static void main(String args[]) throws SQLException {
//Registering the Driver
DriverManager.registerDriver(new com.mysql.jdbc.Driver());
//Getting the connection
String mysqlUrl = "jdbc:mysql://localhost/mydatabase";
Connection con = DriverManager.getConnection(mysqlUrl, "root", "password");
System.out.println("Connection established......");
//Creating the Statement
Statement stmt = con.createStatement();
//Query to alter the table
String query = "ALTER TABLE Sales Drop ID";
//Executing the query
stmt.executeUpdate(query);
System.out.println("Column Deleted......");
}
}Output
Connection established...... Column Deleted......
Since we have deleted one column, if you retrieve the contents of the Sales table using the SELECT command you can observe only 6 (no column named id) columns as:
mysql> select * from Sales; +-------------+--------------+--------------+--------------+-------+----------------+ | ProductName | CustomerName | DispatchDate | DeliveryTime | Price | Location | +-------------+--------------+--------------+--------------+-------+----------------+ | Key-Board | Raja | 2019-09-01 | 05:30:00 | 7000 | Hyderabad | | Earphones | Roja | 2019-05-01 | 05:54:28 | 2000 | Vishakhapatnam | | Mouse | Puja | 2019-03-01 | 04:26:38 | 3000 | Vijayawada | | Mobile | Vanaja | 2019-03-01 | 04:26:35 | 9000 | Chennai | | Headset | Jalaja | 2019-04-06 | 05:19:16 | 6000 | Delhi | +-------------+--------------+--------------+--------------+-------+----------------+ 5 rows in set (0.00 sec)
Updated on: 30-Jul-2019
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