Category Archives: Java

Unable to launch the Java Virtual Machine Located at path: ..\..\jdk\jre\bin\client\jvm.dl

On running Jdevloper for first time you may see the below error

Unable to launch the Java Virtual Machine
Located at path:

1. go to Control Panel->System->Advanced System Settings->Environmental Variables
2. Update the ‘Path’ setting to include the following directory: ‘<jdev home dir>\jdevbin\jdk\bin’
3. Reopen the jDeveloper.


Oracle apps Forms not opening with error message ClassNotFoundException FormsLauncher.class

I came across a Error with a new laptop while opening the forms.

I had java 1.6 update 27 and firefox 34. When I tried to open java it was not opening after trying some things then my forms was opened.

Below are the steps

1.Remove all Java versions. Try to install current version of java in my case it is 8 update 172

2.Try to have Firefox ESR version or Recomended IE version. In my case Firefox ESR 52.8.0

3. Disable TLS in Java: In newer Java Versions you have to disable by, Go to Java control Panel> Goto Advanced Tab> Click General or Security Tree. > If you see TLs 1.1 or TLS 1.2 uncheck them.

4. In Internet Explorer Go to Internet Options> Advanced> Scroll down to Security Disable / Un check all Use TLS 1.0, Use TLS 1.1 and Use TLS 1.2.

Note: Firefox ESR 60 will not support java plugin as of now.

Opening eclipse with different JVM version

Sometimes we have a requirement that the eclipse has to be started by a different java version. So in order to do that we have to do that we have to edit the configuration file in eclipse.

Step 1 :

Open eclipse config file eclipse.ini in your Eclipse folder.


  • Add -vm yourPath\Java\jre6\bin\javaw.exe like in the screenshot below
  • Eclipse-ini-file-edit

Thank You



Why do we use Class.forName to register Drivers

This code is forcing the class representing the MySQL driver to load and initialize. In Java, a class is not loaded unless it is necessary that the class gets loaded. Since JDBC code usually never directly references the driver, it wouldn’t get loaded without Class.forName (or some other equivalent alternatives).

Note that it is necessary to both load and initialize the class, which are 2 different things.

static {
    try {
        java.sql.DriverManager.registerDriver(new Driver());
    } catch (SQLException E) {
        throw new RuntimeException("Can't register driver!");

Also, note that it is not necessary to call .newInstance() — the static initializer of the Driver already registers itself as a JDBC driver.

Finally, note that with the Service Loader API it is usually not necessary to call Class.forName() to load the driver: it can be loaded automatically.



Thank you for Reading

Validating Email, Mobile, Name in Java using Regex

This program validates Email, Mobile, Name in Java using Regex. We have to import Matcher, Pattern in order to use the classes. Regex is very simple and easy way to validate.

import java.util.regex.Matcher;
import java.util.regex.Pattern;

public class Class1 {
public Class1() {
static Pattern pattern=null;
static Matcher matcher=null;
public static void main(String[] args) {
System.out.println(Class1.nameValidation(“Gowtham Raam”));
// System.out.println(Class1.addressValidation(“213, Tecci Park, First Floor, Sholinganallur, chennai “));

Class1 class1 = new Class1();

public static String emailValidation(String email)
String patternvalidation=”^[_A-Za-z0-9-\\+]+(\\.[_A-Za-z0-9-]+)*@”+”[A-Za-z0-9-]+(\\.[A-Za-z0-9]+)*(\\.[A-Za-z]{2,})$”;
pattern = Pattern.compile(patternvalidation);
matcher = pattern.matcher(“”);
return (“Pattern is Matched”+email);
return (“Pattern is Not Matched”+email);

public static String nameValidation(String name)
String patternvalidation=”[A-Z][a-z]+( [A-Z][a-z]+)”;// This pattern Validates like “Gowtham Raam” First Letter to be in InitCaps
pattern = Pattern.compile(patternvalidation);
matcher = pattern.matcher(name);
return (“Pattern is Matched”+name);
return (“Pattern is Not Matched”+name);

public static String phonenNumberValidation(String phonenumber)
String patternvalidation=”\\d{3}-\\d{7}”;
//If pattern should be without (-) symbol replace the String by “\\d{10}”
pattern = Pattern.compile(patternvalidation);

matcher = pattern.matcher(phonenumber);
return (“Pattern is Matched”+phonenumber);
return (“Pattern is Not Matched”+phonenumber);


// public static String addressValidation(String phonenumber)
// {
// String patternvalidation=”\\d+\\s+([a-zA-Z]+|[a-zA-Z]+\\s[a-zA-Z]+)”;
// pattern = Pattern.compile(patternvalidation);
// matcher = pattern.matcher(phonenumber);
// if(matcher.matches())
// {
// return (“Pattern is Matched”+phonenumber);
// }
// else
// {
// return (“Pattern is Not Matched”+phonenumber);
// }
// }

Some Fascinating Programs in Java



Program for Eliminating and Sorting Separatly using Collections





* This is a program for Eliminating and Sorting Separatly using Collections



import java.util.ArrayList;

import java.util.Collections;

import java.util.HashSet;

import java.util.Iterator;

public class ElimatingDuplicatesInArrayAndSorting


public static void main(String[] args)


int[] a={5, 5, 6, 7 ,8, 8, 9, 3, 2, 4, 2, 3, 2, 4, 9};

HashSet h=new HashSet();

ArrayList al=new ArrayList();

for(int i=0;i<=14;i++ )


Integer o=new Integer(a[i]);




Iterator itr=h.iterator();




//int u=Integer.parseInt(w);

System.out.println(“Results in Set”+w);

Integer q=new Integer(w);



Iterator iter=al.iterator();




System.out.println(“Results after sorting :”;








Prime Number and number of Prime Number





//import java.


* This is a program for Checking Whether the number is Prime number and if its not a Prime number the program generates the prime number till that number

* @author Gowtham Raam



public class PrimeNumberOrOtherPrimeNos{

public static void main(String[] args)throws Exception {

BufferedReader in=new BufferedReader(new InputStreamReader(;

String r=in.readLine();


int z=Integer.parseInt(r);



System.out.println(“This si a Prime number” +z);







static void wow(int q)



for(int i=2;i<=q;i++)


int count=0;

for(int j=2;j<=i/2;j++)









System.out.println(“This si a Prime number” + i);





static int Prim1(int o)


int count=0;

for(int i=2;i<=o/2;i++)








return 1;


return 0;







Eliminating Duplicates by using Loop




public class UserInputEliminatingDuplicates


public static void main(String args[]) throws Exception


BufferedReader br = new BufferedReader(new InputStreamReader(;

System.out.println(“Enter a  number”);

String a[]=new String[6];

for(int i=0; i<=5;i++)


int count=0;

String s=br.readLine();

for(int j=0;j<=i;j++)












for(int k=0;k<=5;k++)













Oracle Java Intro Program JDBC Implementation 


import java.sql.*;



* – Demonstrates how to Retrieve data from Oracle

*                    database using Java JDBC.



* Add your JDBC drivers In order to work your Program


class AnothJDBC {

public static void main (String[] args) {

try {


String url = “jdbc:oracle:thin:@”;

Connection conn = DriverManager.getConnection(url,”hr”,”hr”);

Statement st = conn.createStatement();

String sql;

sql = “SELECT * FROM employees”;

ResultSet rs = st.executeQuery(sql);


//int custId = rs.getInt(“EMPLOYEE_ID”);

//String custName = rs.getString(“LAST_NAME”);

System.out.println(rs.getString(“LAST_NAME”)+”          “+rs.getString(“Employee_id”));

//System.out.println(“…CUSTOMER NAME :…”+custName);



} catch (Exception e) {

System.err.println(“Got an exception! “);






Interview Java Programs

Floyds Triangle

class FloydsTriangle
public static void main(String args[]) throws Exception
int num,i,j,k,s=40;
BufferedReader br=new BufferedReader(new InputStreamReader(;
System.out.println(“Enter number “);
System.out.print(” “);

Output is:

Enter number


//Reversing of String program 1
class ReversingStr1
public static void main(String args[])
String st=args[0];
String reversed=ReversingStr1.reverseMe(st);

static String reverseMe(String re)
StringBuilder sb=new StringBuilder();
for(int i=re.length()-1; i>=0;–i)
return sb.toString();

//Reversing of String program 2

class RevesingStr2
public static void main(String args[])
String st=args[0];
String reversed=RevesingStr2.reverseMe(st);
public static String reverseMe(String s)
return “”;
return s.charAt(s.length()-1)+reverseMe(s.substring(0, s.length()-1));

Tower of Hanoi

class TowerOfHanoi
public static void main(String args[])throws IOException
hanoi obj=new hanoi();
BufferedReader br=new BufferedReader(new InputStreamReader(;
System.out.println(“Enter number of rings”);
int N=Integer.parseInt(br.readLine());

class hanoi
void ha(char a,char b,char c,int n)
System.out.println(“WRONG INPUT !!!”);
System.out.println(“Move from “+a+” to “+c);


Enter number of rings
Move from A to C
Move from A to B
Move from C to B
Move from A to C
Move from B to A
Move from B to C
Move from A to C



Connecting java and mysql database

For connecting java application with the mysql database, you need to
follow 5 steps to perform database connectivity.

In this example we are using MySql as the database. So we need to know
following informations for the mysql database:

1. *Driver class: * The driver class for the mysql database is
2. *Connection URL: * The connection URL for the mysql database is
*jdbc:mysql://localhost:3306/test* where jdbc is the API, mysql is
the database, localhost is the server name on which mysql is
running, we may also use IP address, 3306 is the port number and
sonoo is the database name. We may use any database, in such case,
you need to replace the test with your database name.
3. *Username: * The default username for the mysql database is *root*.
4. *Password: * Password is given by the user at the time of installing
the mysql database. In this example, we are going to use root as the

Let’s first create a table in the mysql database, but before creating
table, we need to create database first.

create database test;
use test;
create table emp(id int(10),name varchar(40),age int(3));

Here’s the code

import java.sql.*;
class MysqlCon
public static void main(String args[]){

Connection con=DriverManager.getConnection(“jdbc:mysql://localhost:3306/test”,”root”,”root”);

//here test is database name, root is username and password

Statement stmt=con.createStatement();

ResultSet rs=stmt.executeQuery(“select * from emp”);

System.out.println(rs.getInt(1)+”  “+rs.getString(2)+”  “+rs.getString(3));


}catch(Exception e){ System.out.println(e);}


To connect java application with the mysql database mysqlconnector.jar file is required to be loaded.

We have to manually download the mysqlconnector.jar from the internet and paste the mysqlconnector.jar file in jre/lib/ext folder

Download the mysqlconnector.jar file. Go to jre/lib/ext folder and paste

I use sabayon 10 and path in my os is /etc/java-config-2/current-system-vm/jre/lib/ext/mysqlconnector.jar

Now compile the code and run it.

Thank You for reading

Various methods or types to read input from Console (keyboard) in Java

The below Java program illustrates the types or methods that we can receive inputs from a user

import java.util.Scanner;
class ConsoleReadingDemo {
static String name;
    public static void main(String[] args) {

        BufferedReader reader = new BufferedReader(new InputStreamReader(;
        System.out.print(“Please enter user name : “);
        try {
            name = reader.readLine();
        } catch (IOException e) {
        System.out.println(“You entered : ” + name);

        // ===== In Java 5, Java.util,Scanner is used for this purpose.
        Scanner in = new Scanner(;
        System.out.print(“Please enter user name : “);
        name = in.nextLine();      
        System.out.println(“You entered : ” + name);
        // ====== This feature from Java 6
        Console console = System.console();
        name= console.readLine(“Please enter user name : “);   
        System.out.println(“You entered : ” + name);


Thank you for reading

MySQL Database configuration on linux terminal tutorial

Start the database:

Start the database: /etc/rc.d/init.d/mysqld start
(The script will run mysql_install_db to create a default database in /var/lib/mysql/mysql/ if the mysql init script has never been run before. The install script will not be run again as long as the default database directory exists.)
The database executes as user mysqld and group mysqld.


  • One may manually initialize the database with the command: /usr/bin/mysql_install_db
    Creates system tables in /var/lib/mysql/mysql/
    Only execute the first time MySQL is installed.
  • Databases located in: /var/lib/mysql/
  • Default config file installed by RPM: /etc/my.cnf
    (Ubuntu: /etc/mysql/my.cnf)



Post installation:

  1. Admin user id: root
    Default password: blankThe first task is to assign a password:

    [prompt]$ mysqladmin -u root password 'new-password'

    Note: the following SQL commands will also work:

    mysql> USE mysql;
    mysql> UPDATE user SET Password=PASSWORD('new-password') WHERE user='root';
  2. Create a database: (Creates directory /var/lib/mysql/bedrock)
    [prompt]$ mysqladmin -h localhost -u root -ppassword create bedrock

    (or use SQL command: CREATE DATABASE bedrock;)
    Show all mysql databases: mysqlshow -u root -ppassword


  3. Add tables, data, etc:
    Connect to database and issue the following SQL commands:

    [prompt]$ mysql -h localhost -u root -ppassword
    mysql> show databases;             -- List all databases in MySQL.
    | Database |
    | bedrock  |
    | mysql    |
    | test     |
    mysql> use bedrock;     -- Specify database to connect to. Also refers to path: /var/lib/mysql/bedrock
    mysql> create table employee (Name char(20),Dept char(20),jobTitle char(20));
    mysql> DESCRIBE employee;       -- View table just created. Same as "show columns from employee;"
    | Field    | Type     | Null | Key | Default | Extra |
    | Name     | char(20) | YES  |     | NULL    |       |
    | Dept     | char(20) | YES  |     | NULL    |       |
    | jobTitle | char(20) | YES  |     | NULL    |       |
    3 rows in set (0.03 sec)
    mysql> show tables;
    | Tables_in_bedrock |
    | employee          |
    mysql> INSERT INTO employee VALUES ('Fred Flinstone','Quarry Worker','Rock Digger');
    mysql> INSERT INTO employee VALUES ('Wilma Flinstone','Finance','Analyst');
    mysql> INSERT into employee values ('Barney Rubble','Sales','Neighbor');
    mysql> INSERT INTO employee VALUES ('Betty Rubble','IT','Neighbor');

    Note: Data type used was CHAR. Other data types include:

    • CHAR(M) : Fixed length string. Always stores M characters whether it is holding 2 or 20 characters. Where M can range 1 to 255 characters.
    • VARCHAR(M) : Variable length. Stores only the string. If M is defined to be 200 but the string is 20 characters long, only 20 characters are stored. Slower than CHAR.
    • INT : Ranging from -2147483648 to 2147483647 or unsigned 0 to 4294967295
    • FLOAT(M,N) : FLOAT(4,2) – Four digits total of which 2 are after the decimal. i.e. 12.34 Values are rounded to fit format if they are too large.


  4. Add a user. Use the MySQL SQL console to enter SQL commands. The command mysql with the correct login/password will connect you to the database. The admin tables are stored in the database “mysql”.
    [prompt]$ mysql -h localhost -u root -ppassword
    Welcome to the MySQL monitor.  Commands end with ; or \g.
    Your MySQL connection id is 1 to server version: 3.23.41
    Type 'help;' or '\h' for help. Type '\c' to clear the buffer.
    mysql> USE mysql;
    mysql> SHOW TABLES;
    | Tables_in_mysql |
    | columns_priv    |
    | db              |
    | func            |
    | host            |
    | tables_priv     |
    | user            |
    mysql> INSERT INTO user (Host, User, Password, Select_priv) 
                  VALUES ('', 'Dude1', password('supersecret'), 'Y');
    mysql> FLUSH PRIVILEGES;   -- Required each time one makes a change to the GRANT table
    mysql> GRANT ALL PRIVILEGES ON bedrock.* TO Dude1;
    mysql> FLUSH PRIVILEGES;   -- Required each time one makes a change to the GRANT table
    mysql> quit


    • There is NO space between the -p and the password! You can omit the password and you will be prompted for it.
    • The SQL flush command is equivalent to issuing the command:
      [prompt]$ mysqladmin reload


  5. Test the database:
    mysql> SELECT * from employee;
    | Name            | Dept          | jobTitle    |
    | Fred Flinstone  | Quarry Worker | Rock Digger |
    | Wilma Flinstone | Finance       | Analyst     |
    | Barney Rubble   | Sales         | Neighbor    |
    | Betty Rubble    | IT            | Neighbor    |
    1 row in set (0.00 sec)
    mysql> SELECT name FROM employee WHERE dept='Sales';
    | name          |
    | Barney Rubble |
    1 row in set (0.00 sec)


  6. Quit from the SQL shell:
    [prompt]$ quit


  7. Shutting down the database:
    [prompt]$ mysqladmin -u root -ppassword shutdown       - PREFERRED
    [prompt]$ /etc/rc.d/init.d/mysqld stop
    [prompt]$ service mysqld stop

Documentation in /usr/share/doc/mysql-3.23.41/ (local file)


Users and Security:


Create a database user:

     mysql> CREATE USER david@'localhost' IDENTIFIED BY 'password';


or generate a user by adding them to the user table directly:

     [prompt]$ mysql -h localhost -u root -p 
     mysql> use mysql;
     mysql> INSERT INTO user (Host,User,Password) VALUES('localhost','david',PASSWORD('supersecret'));

Note that the user is defined in the “user” mysql table.


Assign user privileges:

Security and database access is controlled by the GRANT tables. Access to connect to the database and access to process the transaction (table and column access, etc.) are both required. Privileges are searched in the following order:

  1. user table
  2. db and host table
  3. tables_priv
  4. columns_priv

Use the user table to grant connection privileges to database by a user (host, user name and password). Grant database and table access for transaction access. i.e. grant “SELECT”, “UPDATE”, “CREATE”, “DELETE”, “ALTER” etc. permission for database, table, field (columns) or database server access.

Access can be granted by network permissions: GRANT ALL PRIVILEGES on bedrock.* to david@'';
This grants access from nodes – Or the network definitions can reference resolvable names: ‘‘. The host definition of ‘%‘ or ” (null) refers to any host. (..according to the documentation. My experience is that in the mysql.user table use only ‘%’ for “Host” to refer to any host.)

     mysql> GRANT ALL PRIVILEGES on bedrock.* to david@'%';

or (be specific)

     mysql> GRANT SELECT,INSERT,UPDATE,DELETE on bedrock.* to david@'%' identified by 'david';

or (more promiscuous – global privileges rather than database specific)

     mysql> GRANT ALL PRIVILEGES on *.* to david@'%' identified by 'david';

or (be specific by direct assignment in the mysql “Db” table:)

     mysql> use mysql;
     mysql> INSERT INTO db (Host,Db,User,Select_priv,Insert_priv) VALUES('localhost','bedrock','david','Y,'Y');

Note that database specific privileges (eg. Select_priv, Insert_priv, etc) are defined in the “db” mysql table. The mysql “user” table can assign the same (Select_priv, Insert_priv, etc) but global privileges (usually all default to ‘N’).Show privileges: SHOW GRANTS FOR Dude2@'%';

Network security: Use firewall rules (ipchains or iptables) to block internet access to port 3306. (default port used by MySQL)

Note: I have found that when adding access from “anywhere” (‘%’), the MySQL database table ‘user’ requires two entries, ‘localhost’ and ‘%’. Also, it is typically safer to allow more privileges to those with ‘localhost’ access than to users from ‘%’ (“anywhere”).


Passwords and connecting to the databse:

  • Connect: [prompt]$ mysql -h host_name -u user_name -ppassword
  • Using default blank password: [prompt]$ mysql -h localhost -u root -p
    If a password is required, you will be prompted. Note, blank passwords are a security hole which has already lead to one mySQL internet worm. Change any default blank passwords.
  • Delete null/blank users: DELETE FROM user WHERE User = '';
  • Beware of open access permissions from hosts '%': SELECT * FROM db WHERE Host = '%';
  • Change a password:
        [prompt]$ mysqladmin -u root -p password new-password

    You will be prompted to enter the old root password to complete this command.

        [prompt]$ mysqladmin -u root -pold-password password new-password


        mysql> SET PASSWORD FOR root@'localhost' = PASSWORD('supersecret');
        mysql> FLUSH PRIVILEGES;
  • As an added security precaution it is wise to delete any user id not used. i.e. any defaults generated for demonstration purposes.
  • Note that the default port used by MySQL is 3306. This can be protected with firewall rules. See the YoLinux IpTables tutorial.

Debian/Ubuntu upgrades: Note that the Debian/Ubuntu distribution will have an additional file /etc/mysql/debian.conf. This file holds a password for the user “debian-sys-maint” which is used by the install tool dpkg to perform database upgrades. This can also be used in emergencies if you forget the root password. It is also a security hole if the file is available to others.

[Potential Pitfall]: It is very easy to make mistakes which get entered into important tables. If you enter the command twice you may have one incorrect and one correct entry. Look at the table data after a mistake to see what happened in case it needs to be fixed.

mysql> USE mysql;
mysql> SELECT User,Password,Host from user;
| User  | Password         | Host       |
| root  | 99a1544eb571ad63 | localhost  |
|       |                  | localhost  |
| Dude1 | 81a10dba5f6f2144 |            |
| Dude1 |                  |            |
| Dude2 | 92b10dba6f7f3155 | %          |
5 rows in set (0.00 sec)
mysql> DELETE FROM user WHERE User='' AND Host='localhost';
mysql> DELETE FROM user WHERE User='Dude1' AND Password='';
mysql> QUIT

User entries may also be found in the table mysql.db.

mysql> DELETE FROM db WHERE User='Dude3' AND Host='localhost';

[Potential Pitfall]: Any changes (UPDATE) to the user table will require a “FLUSH PRIVILEGES” before the changes will be effective.

mysql> UPDATE user SET Host='%' WHERE User='Dude2';

This will allow a connection with mysql client from any host:
[prompt]$ mysql -u Dude2 -ppassword -h


MySQL root password recovery:

  1. As Linux system root user stop the database process: /etc/init.d/mysql stop
    (or: service mysql stop)
  2. Start MySQL in safe mode and skip the use of the “grant tables”: /usr/bin/mysqld_safe --user=mysql --socket=/var/lib/mysql/mysql.sock --pid-file=/var/run/mysqld/ --datadir=/var/lib/mysql --skip-grant-tables --skip-networking &
  3. Reset the MySQL root password: mysqladmin -u root flush-privileges password newpassword
  4. Stop MySQL running in safe mode: kill `cat /var/run/mysqld/`
  5. Start MySQL: /etc/init.d/mysql start
  6. The new MySQL root password can now be used: mysql -u root -p
    Respond with the password: newpassword


Disabling networking:

If your configuration is a web server interacting with a mySQL database running on the same “localhost” then one may turn off network access to tighten security. Edit shell script:

  • /usr/bin/safe_mysqld (Fedora Core 3)
  • /usr/bin/mysqld_safe (Red Hat Enterprise Linux 4 – MySQL 5.0)
  if test -z "$args"
    $NOHUP_NICENESS $ledir/$MYSQLD $defaults --basedir=$MY_BASEDIR_VERSION \
                      --datadir=$DATADIR $USER_OPTION --pid-file=$pid_file \
                      --skip-networking --skip-locking >> $err_log 2>&1
    eval "$NOHUP_NICENESS $ledir/$MYSQLD $defaults --basedir=$MY_BASEDIR_VERSION \
                      --datadir=$DATADIR $USER_OPTION --pid-file=$pid_file \
                      --skip-networking --skip-locking $args >> $err_log 2>&1"

Add the flag “--skip-networking” marked in bold.

Mysql 5.0 configuration: Networking is disabled by default on the default Red Hat and Ubuntu installation.

Red Hat/CentOS: To enable remote database access, add the “bind-address” with the public IP address to the file: /etc/my.cnf. To force local access only without remote access, set the “bind-address” to


Restart the database after making changes.

Ubuntu: To enable remote database access, comment out (or remove) the following line with a “#” in the file: /etc/mysql/my.cnf


bind-address           =


Restart the database after making changes.


A firewall rule can further restrict access to a single server (eg web server at

/sbin/iptables -A INPUT -i eth0 -s -p tcp --destination-port 3306 -j ACCEPT

or LAN only access:

/sbin/iptables -A INPUT -i eth0 -s -p tcp --destination-port 3306 -j ACCEPT


MySQL Admin Commands:


  • Statistics: [prompt]$ mysqladmin version
  • List database environment: [prompt]$ mysqladmin variables
  • Show if database is running: [prompt]$ mysqladmin ping
  • Show databases available:
    [prompt]$ mysqlshow
    | Databases |
    | bedrock   |
    | mysql     |
    | test      |


    mysql> SHOW DATABASES;
  • Delete database: mysql> drop database bedrock;
  • Show list of active threads in server:
    [prompt]$ mysqladmin -h localhost -u root -p processlist
    | Id | User | Host      | db | Command | Time | State | Info             |
    | 15 | root | localhost |    | Query   | 0    |       | show processlist |
  • Delete a database: [prompt]$ mysqladmin drop database-name
  • Execute SQL from Linux command line interface:
    [prompt]$ mysql -h localhost -u root -p -e "select host,db,user from db" mysql
  • Execute SQL command file from Linux command line interface:
    [prompt]$ mysql -h localhost -u root -p database-name < text-file-with-sql-statements.sql
  • Loadtest (benchmark) the system:
    [prompt]$ cd sql-bench
    [prompt]$ run-all-tests
    [prompt]$ mysql -vvf test < ./tests/auto_increment.tst


Sample SQL:

SQL requests are either administrative or data-related. The following are sample SQL segments and are not necessarily pertinent to the previous example:

Create and use a new database named “bedrock”:

mysql> CREATE DATABASE bedrock;   -- Comments follow a double dash
mysql> USE bedrock;

Create and populate table with data:

mysql> CREATE TABLE retired_employee (
                    Name char(20) DEFAULT '' NOT NULL,
                    Dept char(10) DEFAULT '' NOT NULL,
                    JobTitle char(20),
                    UNIQUE name_dept (Name,Dept)
mysql> CREATE UNIQUE index name_dept on employee (name,dept); -- avoids duplicate keys
mysql> INSERT INTO employee VALUES ("Jane Smith","Sales","Customer Rep");
mysql> INSERT INTO employee VALUES ('Jane Smith','Sales','Account Manager');
mysql> INSERT INTO employee VALUES ('Jane Smith','Engineerin','Manager');
mysql> UPDATE employee SET dept='HR' WHERE name='Jane Smith';
mysql> CREATE TABLE pet (
                 name VARCHAR(20), 
                 owner VARCHAR(20), 
                 species VARCHAR(20), 
                 sex CHAR(1), 
                 birth DATE, 
                 death DATE);

Add constraints to a table:

-- Use "auto_increment" integer column:
mysql> ALTER TABLE employee DROP INDEX name_dept;  -- get rid of index

Interrogate an existing database:

mysql> USE bedrock;
mysql> SELECT DATABASE();  -- returns current database. eg. bedrock
mysql> SELECT NOW();
mysql> SELECT USER();
mysql> DESC employee;
mysql> SHOW CREATE TABLE employee;  -- show command used to generate table
mysql> SHOW INDEX FROM employee;
mysql> SELECT DISTINCT dept FROM  bedrock;
mysql> SELECT * FROM  bedrock WHERE Name  LIKE "B%y";  -- "%" match any char: Gives Betty and Barney
mysql> SELECT * FROM  bedrock WHERE Name LIKE "B___y";  -- "_" match space: Gives Betty but not Barney
mysql> SELECT * FROM  bedrock WHERE Name RLIKE "^Betty$";  -- "^" match beginning. "$" to denote end of string
mysql> SELECT COUNT(*) FROM employee;  -- Number of records returned
mysql> SELECT Name, COUNT(*) FROM employee WHERE Name LIKE "B%y";  -- Return Names and number of records returned
mysql> SELECT * FROM pet WHERE species = "snake" OR species = "bird";
mysql> SELECT * FROM pet WHERE species = "dog" AND sex = "f";
mysql> SELECT * FROM pet WHERE birth >= "1998-1-1";
mysql> SELECT name, birth FROM pet ORDER BY birth DESC;
mysql> SELECT * FROM pet WHERE name LIKE "b%";
mysql> SELECT * FROM pet WHERE name REGEXP "^b";
mysql> SELECT species, COUNT(*) FROM pet GROUP BY species;
mysql> SELECT MAX(article) AS article FROM shop;
mysql> SELECT * FROM employee WHERE name LIKE "%Sm%";
mysql> SELECT * FROM employee WHERE name REGEXP "^Ja";

Database cleanup:

mysql> DROP TABLE employee;
mysql> DROP DATABASE bedrock;

See section 3 of MySQL manual for more examples.

Tip: Execute a shell command from the MySQL client interface, use either option:

  • system ls -l
  • \! ls -l

Example: execute the “ls” command to list files from the MySQL client.


Loading Data into the MySQL database:

Loading a SQL file into MySQL:

Import SQL file from MySQL client command line:

  • mysql> source file.sql
  • mysql> \. file.sql

The SQL file may have schema generation statements like CREATE TABLE ... or data load statements like INSERT INTO ... . The statements in the SQL file will be executed as if they were being specified at the MySQL client command line interface.


One may import data into the MySQL database from SQL files or “load” data from CSV or tab delimited files using the LOAD command:

Loading CSV or tab delimeted files into MySQL:

LOAD DATA LOCAL INFILE” vs “LOAD DATA INFILE“: The term “LOCAL” pertains to whether the file is local to the MySQL client. Without the keyword “LOCAL“, the datafile must reside on the same computer as the database server. The location of the client in this case would be irrelevant. The “LOAD DATA INFILE” has many file permission pitfalls and is thus trickey. In fact I have never been sucessful using this method with a user directory.


Load a tab delimited file into the database:

Command: LOAD DATA LOCAL INFILE 'file.dat' INTO TABLE employer;

Input tab delimited file: file.dat

Fred Flinstone  Quarry Worker   Rock Digger
Wilma Flinstone Finance Analyst 
Barney Rubble   Sales   Neighbor
Betty Rubble    IT      Neighbor


  • The number of tab delimeted fields MUST match the number and order of fields in the database.


Load a comma delimited file (CSV) into the database:




  • MS/Windows generated files will have lines terminated by “\r\n”.
  • Linux/Unix generated files will have lines terminated by “\n”.
  • File locations on database server must be absolute path names, relative path or relative to the mysqld process owner’s home directory (typically /var/lib/mysql/). File locations on the client may be fully qualified or relative to the current mysql client directory.
    • Fully qualified: /tmp/TableData.csv
    • Relative to current mysql client directory: ./TableData.csv
      (Verify current directory: mysql> \! pwd)
    • Database process owner home directory: TableData.csv
      (Actual: /var/lib/mysql/TableData.csv)
  • Text strings often are encapsulated by quotes so that the strings may contain a comma without representing a new field.

[Potential Pitfalls]:

  • ERROR 13 (HY000): Can't get stat of '/tmp/TableData.csv' (Errcode: 13)
    The fils is local and you have not specified the “LOCAL” directive.
  • ERROR 29 (HY000): File '/var/lib/mysql/test/TableData.csv' not found (Errcode: 2)
    Error from command LOAD DATA INFILE 'TableData.csv' INTO ... where the file is assumed to be read from the /database-process-home-directory/mysql-database-name/TableData.csv
    (Note: Database name “test” is being used.)
  • ERROR 1045 (28000): Access denied for user 'user1'@'%' (using password: YES)
    ERROR 2 (HY000): File '/tmp/TableData.csv' not found (Errcode: 2)
    Error from command LOAD DATA INFILE '/tmp/TableData.csv' INTO .... This is a common pitfall, trying to load a file located on the database server remotely from a client. Getting the file permissions correct is difficult. Avoid this method. Use the LOAD DATA LOCAL INFILE instead of the LOAD DATA INFILE method (it is so much easier).

Also look at the mysqlimport command.

Dump/Backup/Transfer Database:

The mysqldump command will read the mySQL database and generate a SQL command text file. This allows data to be migrated to other versions of mySQL (i.e. upgrade from typical Red Hat (RH7.x to FC3) mySQL release 3.23.58 to a more advanced mySQL 4.1 or 5.0) or to other SQL databases. SQL command file generated can create tables, insert data, ….


Option Description
Dump all the databases.
Dump the specified databases.
Specify host to connect to.
Specify password. If you do not specify a password, then you will be queried.
Specify user. Defaults to current user logged in.
–opt Same as: –add-drop-table –add-locks –all –extended-insert –quick –lock-tables
–add-drop-table Add a “drop table” SQL statement before each “create” SQL statement.
–add-locks Add “lock” SQL statements around “insert” SQL statements.
Include all mySQL specific SQL “create” options.
Allows utilization of the new, much faster INSERT syntax. Database you are migrating to must support this notation.
Don’t buffer query, dump directly to stdout.
Lock all tables for read.
Display command line options.


  • Dump database to a file:
    • Dump specified database:
      mysqldump --opt database > db-dump-file.sql
    • Dump specified table in database:
      mysqldump --opt database table-name > db-dump-file.sql
    • Dump multiple databases:
      mysqldump --opt --databases database1 database2 database3 > db-dump-file.sql
    • Dump everything:
      mysqldump --opt --all-databases > total-db-dump-file.sql
      mysqldump -u user-id -h host-name --opt --all-databases > total-db-dump-file.sql

    [Potential Pitfall]: If you experience the following error:

    mysqldump: Got error: 1016: Can't open file: 'Database-Name' (errno: 145) when using LOCK TABLES

    Fix with the following command: mysqlcheck -r -u root -p Database-Name

  • Import dumped file:
    mysql database < db-dump-file.sql
  • Export from one database and import to another:
    • Transfer specifed database from one database to another:
      mysqldump --opt database | mysql --host=host-name -C database

Man Page:

Upgrading to 4.1:


Restore MySql Database:

Restore using dump generated by mysqldump above:

  • mysql -h host-name -u user-id -psupersecretpassword < total-db-dump-file.sql
  • mysql database-name -h host-name -u user-id -psupersecretpassword < db-dump-file.sql


System Notes:

[Potential Pitfall]: Ubuntu mysql 5.0 database migration – When migrating the mysql database by copying files from /var/lib/mysql/... and /etc/mysql/... from one system running Ubuntu 6.11 to 8.04, I got nebulous error message in /var/log/syslog. The root cause of the problem was apparmor. If turing off apparmor (/etc/init.d/apparmor stop) allows your database to start and function properly, then go fix your apparmor security rules in /etc/apparmor.d/usr.sbin.mysqld. Also note that you must use the newer script /etc/mysql/debian-start from release 8.04 after copying /etc/mysql/....

Note: Debian and Ubuntu distributions manage mysql package upgrades using a mysql user debian-sys-maint which has its information located in /etc/mysql/debian.cnf. If you ever forget your mysql root password, you can always get back into the mysql database using the user debian-sys-maint and its password held in /etc/mysql/debian.cnf.


Building MySql from source: (on Linux)


  • C compiler: 2.95.2 or later. (Check with the command: rpm -q gcc)

Compile and install: (as root)

  • Downloaded source from
  • Expand tar file: tar xzf mysql-4.1.16.tar.gz
  • cd mysql-4.1.16
  • ./configure --prefix=/opt/mysql --sysconfdir=/opt/etc --localstatedir=/opt/var/mysql --with-unix-socket-path=/opt/tmp/mysql.sock
    (Use the command ./configure --help to see all options.)
    This should create an installation which will not clobber an existing RPM mySQL installation.
  • make
  • make install
  • Create mysql config file: cp support-files/my-medium.cnf /opt/var/my.cnf
  • Create user/group mysql
    • Test if user/group mysql already exists: groups mysql
    • Create group: groupadd mysql
    • Create user: useradd -g mysql -M -r -d /opt/lib/mysql -s /sbin/nologin -c "MySQL Server" mysql
  • chown -R mysql:mysql /opt/var/mysql


  • Install default database: /opt/mysql/bin/mysql_install_db --user=mysql
    Since this command is run as root, specify the --user option to operate command as user mysql.
    Creates help database with SQL script: /opt/mysql/share/mysql/fill_help_tables.sql
  • Start mySQL database: /opt/mysql/bin/mysqld_safe --user=mysql &
  • /opt/mysql/bin/mysqladmin -u root password 'new-password'
  • /opt/mysql/bin/mysqladmin -u root -h yoserver2 password 'new-password'
  • See tutorial above for use and administration.
  • Check defaults: (Defaults from config file: /opt/var/my.cnf)
    • /opt/mysql/bin/my_print_defaults --config-file=my client mysql
    • /opt/mysql/bin/my_print_defaults --config-file=my client mysql mysql_install_db


Commands/Man pages:


  • isamchk – Check and repair of ISAM tables.
  • isamlog – Write info about whats in a nisam log file.
  • msql2mysql
  • my_print_defaults
  • myisamchk
  • myisamlog
  • myisampack
  • mysql – text-based client for mysqld, a SQL-based relational database daemon
  • mysql_config
  • mysql_convert_table_format
  • mysql_find_rows
  • mysql_fix_privilege_tables
  • mysql_install_db
  • mysql_setpermission
  • mysql_zap – a perl script used to kill processes
  • mysqlaccess – Create new users to mysql.
  • mysqlbinlog
  • mysqlbug
  • mysqlcheck
  • mysqld_multi – Used for managing several mysqld processes running in different UNIX sockets and TCP/IP ports.
  • mysqldump – text-based client for dumping or backing up mysql databases , tables and or data.
  • mysqldumpslow
  • mysqlhotcopy
  • mysqlimport
  • mysqlshow – Shows the structure of a mysql database (databases,tables and columns)
  • mysqltest
  • pack_isam
  • perror – used to display a description for a system error code, or an MyISAM/ISAM table handler error code.
  • replace – A utility program to replace changes strings in place in files or on the standard input.
  • resolve_stack_dump
  • resolveip


  • mysqladmin – A utility for performing administrative operations
  • safe_mysqld – The recommended way to start a mysqld daemon on Unix.


Admin GUI Tools: