JDBC Select Count example
In this tutorial we will learn how work COUNT() in query with mysql JDBC driver.
In this tutorial we will learn how work COUNT() in query with mysql JDBC driver.JDBC Select Count example
In this tutorial we will learn how work COUNT() in query with mysql JDBC driver. This tutorial COUNT(*) returns a count of the number of rows retrieved, whether or not they contain NULL values. Table of user :
Mysql query "SELECT COUNT(*) FROM user" count number of rows, whether or not they contain NULL values. So this query count number of rows 5. If change the COUNT(*) to COUNT(user_name) then count number of rows 4 that contain user_name it ignore the user_name (NULL) value . The code of "SelectCount.java" is:
import java.sql.DriverManager;
import java.sql.Connection;
import java.sql.Statement;
import java.sql.SQLException;
import java.sql.ResultSet;
public class SelectCount{
// JDBC driver name and database URL
static String driverName = "com.mysql.jdbc.Driver";
static String url = "jdbc:mysql://localhost:3306/";
// defined and set value in dbName, userName and password variables
static String dbName = "testjdbc";
static String userName = "root";
static String password = "";
public static void main(String[] args){
// create Connection con, and Statement stmt
Connection con=null;
Statement stmt=null;
try{
Class.forName(driverName).newInstance();
con = DriverManager.getConnection(url+dbName, userName, password);
try{
stmt = con.createStatement();
String query = "SELECT COUNT(*) FROM user";
ResultSet rs=stmt.executeQuery(query);
//Extact result from ResultSet rs
while(rs.next()){
System.out.println("COUNT(*)="+rs.getInt("COUNT(*)"));
}
// close ResultSet rs
rs.close();
} catch(SQLException s){
s.printStackTrace();
}
// close Connection and Statement
con.close();
stmt.close();
}catch (Exception e){
e.printStackTrace();
}
}
}
Program Output :
| F:\jdbc>javac SelectCount.java F:\jdbc>java SelectCount COUNT(*)=5 F:\jdbc> |
