Before deleting a column in a table, first is need to connect the java application to the database. Java has its own API which JDBC API which uses JDBC drivers for database connections. Before JDBC, ODBC API was used but it was written in C which means it was platform-dependent. JDBC API provides the applications to JDBC connection and JDBC driver provides manager to driver connection.
Algorithm: Always remember these 7 thumb golden steps to deal with JDBC in order to deal with the database and between App(Main) class and connection class of it.
- Importing the database
- Registering the Java class
- Establishing a connection
- Creating a statement
- Executing the query
- Process the results
- Closing connection
Procedure: to delete a column in a table from the database created using JDBC is as follows:
Step 1: Loading “mysqlconnector.jar” in the program.
Step 2: Creating a database and adding a table with records
- Using MySQL
- ‘cmd’ Driver
- DriverManager()
- Connection()
- Statement()
- Resultset() which the classes provided by JDBC API
- Further 5 steps are demonstrated in the java program. (App class or Main class) of the Connection class.
Implementation: Java program using JDBC to delete a Column in a Table
Java
// Java program using JDBC to// Delete a Column in a Table// Step 1: Importing database filesimport java.sql.*;public class GFG { // URL that points to mysql database // DB stands for database static final String url // Main driver method public static void main(String[] args) throws ClassNotFoundException { // Try block to check exceptions try { // Step 2: Load and Register drivers // Class.forName() method is user for // driver registration with name of the driver // as argument that used MySQL driver Class.forName("com.mysql.jdbc.Driver"); // Step 3: Create a connection // getConnection() establishes a connection // It takes url that points to your database // username and password of MySQL connections as // arguments Connection conn = DriverManager.getConnection( url, "root", "1234"); // create.Statement() creates statement object // which is responsible for executing queries on // table Statement stmt = conn.createStatement(); // Executing the query student is the table // name & address is column // Step 4: Create a statement String query = "ALTER TABLE student Drop address"; // Step 5: Execute the query // executeUpdate() returns number of rows // affected by the execution of the statement int result = stmt.executeUpdate(query); // Step 6: Process the results // if result is greater than 0 // it means values has been added if (result > 0) System.out.println( "A column from the table is deleted."); else System.out.println("unsuccessful deletion "); // Step 7: Closing connection conn.close(); } // Catch block to handle exceptions catch (SQLException e) { // Print the exception System.out.println(e); } }} |
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