--Before executing java program execute these database scripts >
create table EMPLOYEE(id number(4),name varchar2(22));
insert into EMPLOYEE values(1,'ankit');
insert into EMPLOYEE values(2,'rohit');
commit;
--If table already exists then execute the DROP command >
drop table EMPLOYEE;
Full Programs JDBC- Execute DELETE query using Statement's execute and getUpdateCount method in java
import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.SQLException;
import java.sql.Statement;
/** Copyright (c), AnkitMittal JavaMadeSoEasy.com */
public class StatementDeleteTest {
public static void main(String... arg) {
Connection con = null;
Statement stmt = null;
try {
// registering Oracle driver class
Class.forName("oracle.jdbc.driver.OracleDriver");
// getting connection
con = DriverManager.getConnection(
"jdbc:oracle:thin:@localhost:1521:orcl",
"ankit", "Oracle123");
System.out.println("Connection established successfully!");
stmt = con.createStatement();
/*
execute() method returns true
if returned result is a ResultSet object and
execute() method returns false
if returned result is a update count
*/
//execute delete query
boolean result = stmt.execute("DELETE from EMPLOYEE where id=2 ");
System.out.println(result ? "returned result is a ResultSet object"
: "returned result is a update count"); // false
int numberOfRowsDeleted = stmt.getUpdateCount();
System.out.println("numberOfRowsDeleted = " + numberOfRowsDeleted);
} catch (ClassNotFoundException e) {
e.printStackTrace();
} catch (SQLException e) {
e.printStackTrace();
}
finally{
try {
if(stmt!=null) stmt.close(); //close Statement
if(con!=null) con.close(); // close connection
} catch (SQLException e) {
e.printStackTrace();
}
}
}
}
/*OUTPUT
Connection established successfully!
returned result is a update count
numberOfRowsDeleted = 1
*/
|
Must Know :
By default connection is auto-commit, so all delete queries will be committed automatically by java connection.
(Also must know : delete is a DML(Data Manipulation Language) command, queries are not committed automatically in database)
We may stop connection from doing auto-commits by setting auto-commit to false using > con.setAutoCommit(false);
Well in that we may commit transactions any time using con.commit();
Also, We may set connection back to default behavior of doing auto-commit by using > con.setAutoCommit(true) or simply using con.setAutoCommit();
But what will be benefit of using con.setAutoCommit(false)?
If any transaction goes wrong than we may halt execution further related transactions before calling con.commit() and call con.rollback() in catch block.
NOTE : Statement is suitable for executing DDL commands - create, drop, alter and truncate. This article demonstrates that Statement can also be used to serve the purpose.
We must prefer PreparedStatement, as it is suitable for executing DML commands - SELECT, INSERT, UPDATE and DELETE.
RELATED LINKS>
java.sql.PreparedStatement - using executeUpdate and executeQuery methods - CREATE, SELECT, INSERT, UPDATE and DELETE
JDBC- Insert/Store/save FILE in database
JDBC- Batch PreparedStatement example- Execute INSERT query(DML command) using PreparedStatement's addBatch() and executeBatch() methods in java
Execute database STORED PROCEDURE - IN parameter, OUT parameter and IN OUT parameter || call FUNCTION from java