Oracle SQL Command Line Tricks for Beginners

This is Oracle SQL Command Line Tricks for beginners. Simply do the following:

1. First Open "Run SQL Command Line"
2. Type conn username/password
 For example: conn SYSTEM/vijaya
or simply you can type: conn
Then, it will ask for username. It will show "Enter user-name:", type "vijaya"
Then, it will ask for password. Enter your password: Vijaya
Voila! You're connected.

Type:
select * from student
It will display "2" because you didn't enter semicolon after sql query. enter semicolon.

Then, you will see the table data from student.

If you don't have any table, you can simply create a database using:
create table student(
id int not null,
name varchar(20) not null,
marks int,
primary key (id)
);

To insert new data, you can simply do the following:
insert into student values (1, 'Vijaya', 80);

Or, you can insert by doing:

insert into student values (&id, '&name', &marks);
then, it will display:
Enter value for id: (enter your id) eg. 2
Enter value for name: (enter your name) eg. Hari
Enter value for marks: (enter your marks) eg. 78
Hit Enter,
then it will display:
1 row created.

If you want to commit your changes, type: commit; and hit enter.
then, you will see "commit complete" message.

If you want to insert multiple rows into the table, you can simply type forward slash "/" and hit enter.
It will repeat the same message again:
Enter value for id: (enter your id)
Enter value for name: (enter your name)
Enter value for marks: (enter your marks)
Hit Enter.

This is tested on Windows 10, Oracle XE 11g.

MySQL JDBC jar File on OpenSUSE

First Method:
1. sudo zypper install mysql-connector-java (or go to Software Management and search for jdbc, you will find mysql-connector-java package).
2. Once it's installed, you'll have the file /usr/share/java/mysql-connector-java.jar (/usr/share/java/mysql.jar), which is an indirect symlink to the actual jar file.
3. in Eclipse, do this as: Project -> Properties -> Java Build Path -> Libraries -> Add External JARs -> select /usr/share/java/mysql-connector-java.jar


Or, Second Method:

Download the MySQL JDBC connector from http://www.mysql.com/downloads/connector/j/5.1.html.
[Platform Independent (Architecture Independent), Compressed TAR Archive]
Extract the JDBC driver JAR file from the downloaded file; for example:
tar zxvf mysql-connector-java-5.1.39.tar.gz 

Add the JDBC driver, renamed, to the relevant server; for example:
$ sudo cp mysql-connector-java-5.1.39/mysql-connector-java-5.1.39-bin.jar /usr/share/java/mysql-connector-java.jar
If the target directory does not yet exist on this host, you can create it before copying the .jar file; for example:
$ sudo mkdir -p /usr/share/java/
$ sudo cp mysql-connector-java-5.1.39/mysql-connector-java-5.1.39-bin.jar /usr/share/java/mysql-connector-java.jar

I did the first method.

******************************
Test if JDBC Connection is Suffessful:

import java.sql.*;  
class JdbcTest{  
public static void main(String[] args) throws Exception {  
System.out.println("Connecting database...");

Connection connection = null;
String url = "jdbc:mysql://localhost:3306/cs_project";
String username = "root";
String password = "vijaya";
try {
Class.forName("com.mysql.jdbc.Driver");  
connection = DriverManager.getConnection(url, username, password);
System.out.println("Connection Successful.");
// Success.
} catch (SQLException e) {
// Fail.
System.out.println("Connection Failed."+e);
} finally {
if (connection != null) try { connection.close(); } catch (SQLException ignore) {}
}
}  
}  

Install Sublime Text on OpenSUSE

Download Sublime Text tarball from the following link:
http://www.sublimetext.com/3
(Ubuntu 64 bit - also available as a tarball for other Linux distributions.)

Extract the downloaded file sublime_text_3_build_3114_x64.tar.bz2

Once unpacked, you will get a directory called “sublime_text_3″, inside this directory you will see a list files that required by Sublime Text to run.
For example, go to the folder sublime_text_3 and open new terminal window and type ./sublime_text, sublime text editor will open. But everytime, doing this way to open a sublime text editor is not a good idea.

For security reason, we move this folder under “/opt” location. For this enter the following command:
sudo mv sublime_text_3 /opt/ 
sudo mv Sublime\ Text\ 3 /opt/ (if folder name is Sublime Text 3)

Next create a symbolic link to call “Sublime Text” from the command line as “sublime”. To do, create a symbolic link under “/usr/bin” as shown below.
sudo ln -s /opt/sublime_text_3/sublime_text /usr/bin/sublime

Now, you are ready to use sublime text. Just type sublime in terminal, sublime text editor will open.

Regular Expression in Java for Email Validation

class RegexTest {
   public static void main(String[] args) {

      String my_regex = "^[a-z0-9._]+@[a-z0-9.-]+\\.[a-z]{2,3}$";
     
      String my_email = "tekendra587@gmail.com";
      Boolean b = my_email.matches(my_regex);
      System.out.println("Email address "+my_email+" is: " + b);
     
      String my_another_email = "user^domain.co.in";
      b = my_another_email.matches(my_regex);
      System.out.println("Email address "+my_another_email+" is: " + b);
   }
}

Changing Extension to Multiple Files on OpenSUSE

To change extension of multiple files (suppose all .txt files to .jpg), open terminal and execute the following command:

rename txt jpg *.txt

Explanation: here, it replaces the every occurrence of txt to jpg in all file matching "*.txt"

To change back to .txt, execute the following command:

rename jpg txt *.jpg

Print Object in Java

To print objects in Java, we can use toString() method.
toString() method belongs to object class.

class Student{
String name;
int id;
String city;

Student(String name, int id, String city){
this.name = name;
this.id = id;
this.city = city;
}
public String toString(){
return " Name: "+name + " id: "+id + " city: "+city;
}

public static void main(String[] args){
Student S1 = new Student("Dj", 111, "Irving");
Student S2 = new Student("Rabi", 222, "Dallas");
System.out.println(S1);
System.out.println(S2);
}
}

Now, the output will be:
               Name: Dj id: 111 city: Irving
Name: Rabi id: 222 city: Dallas

If we don't use the toString() method and directly print the object, we get some garbage values that we cannot understand.

ArrayList Concept in Java [2D ArrayList Java]:

import java.util.*;
class TestArrayList {
 public static void main(String args[]) {
  Scanner input = new Scanner(System.in);

  ArrayList al = new ArrayList();
  for (int i = 0; i < 2; i++) {
   System.out.print("Enter food :"); //example: Momo, 2
   String user_input = input.nextLine();
   String formatted_input[] = user_input.split("\\,"); //split into 1 D array
   al.add(formatted_input); //append it to a 2D list
  }

  System.out.println("******************\nMethod 1: to print 2D array list:");
  for (int i = 0; i < al.size(); i++) { //if it is arraylist, we need to use size() instead of .length
   String newarr[] = new String[2];
   newarr = al.get(i); //get subarray in newarr
   System.out.print(newarr[0] + " " + newarr[1] + "\n"); //get 0th and 1th element 
   //if the subarray is large, we need to use another for loop instead of just using 0 and 1
  }

  System.out.println("******************\nMethod 2: to print 2D array list: ");
  for (String[] ob : al) {
   System.out.println(ob[0] + " " + ob[1]);
  }
 }
}