How do I export MySQL database schema into markdown format?

The following code example demonstrate how to export MySQL database schema into markdown table format. We get the table structure information by executing MySQL’s DESCRIBE statement.

The steps we do in the code snippet below:

  • Connect to the database.
  • We obtain the list of table name from the database / schema.
  • Executes DESCRIBE statement for each table name.
  • Read table structure information such as field, type, null, key, default and extra.
  • Write the information into markdown table format and save it into

And here are the complete code snippet.

package org.kodejava.jdbc;

import java.sql.*;
import java.util.ArrayList;
import java.util.List;

public class DescribeMySQLToMarkDown {
    private static final String URL = "jdbc:mysql://localhost/kodejava";
    private static final String USERNAME = "root";
    private static final String PASSWORD = "";

    public static void main(String[] args) {
        String tableQuery = """
                select table_name
                from information_schema.tables
                where table_schema = 'kodejava'
                  and table_type = 'BASE TABLE'
                order by table_name;

        try (Connection connection = DriverManager.getConnection(URL, USERNAME, PASSWORD)) {
            Statement stmt = connection.createStatement();
            ResultSet resultSet = stmt.executeQuery(tableQuery);
            List<String> tables = new ArrayList<>();
            while ( {

            System.out.println(tables.size() + " tables found.");

            try (BufferedWriter writer = new BufferedWriter(new FileWriter(""))) {
                for (String table : tables) {
                    System.out.println("Processing table: " + table);
                    Statement statement = connection.createStatement();
                    ResultSet descResult = statement.executeQuery("DESCRIBE " + table);

                    writer.write(String.format("Table Name: **%s**%n%n", table));
                    writer.write("| Field Name | Data Type | Null | Key | Default | Extra |\n");
                    while ( {
                        String field = descResult.getString("field");
                        String type = descResult.getString("type");
                        String nullInfo = descResult.getString("null");
                        String key = descResult.getString("key");
                        String defaultInfo = descResult.getString("default");
                        String extra = descResult.getString("extra");
                        String line = String.format("| %s | %s | %s | %s | %s | %s |%n",
                                field, type, nullInfo, key, defaultInfo, extra);
            } catch (Exception e) {
        } catch (SQLException e) {

This code snippet will produce something like below. I have tidy up the markdown for a better presentation.

Table Name: **books**

| Field Name | Data Type       | Null | Key | Default | Extra          |
| id         | bigint unsigned | NO   | PRI | null    | auto_increment |
| isbn       | varchar(30)     | NO   |     | null    |                |


Maven dependencies


Maven Central

How do I read MySQL data from Android using JDBC?

This example show you how to connect and read data from MySQL database directly from Android. The following steps and code snippet will show you how to do it.

Add the MySQL JDBC driver into your project dependencies. Open the app/build.gradle file and add the dependency.


dependencies {
    implementation 'mysql:mysql-connector-java:5.1.49'

If you want to connect to MariaDB you can change the JDBC driver dependency using 'org.mariadb.jdbc:mariadb-java-client:1.8.0', also update the JDBC url in the code snippet by replacing mysql with mariadb.

Next, add internet permission to our application in AndroidManifest.xml file.

<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android=""

    <uses-permission android:name="android.permission.INTERNET" />



Let’s connect, read data from the database and display the information on the screen. In the code snippet we create an AsyncTask to read the information from the database. In the doInBackground() method we open a connection to the database, create a PreparedStatement, execute a query, get a ResultSet and read the information from it. We pack the data into a Map and return it.

After the doInBackground() method finish its execution the onPostExecute() method will be called. In this method we take the result, the Map returned by the doInBackground() method, and set the values into the TextView components for display.


import android.annotation.SuppressLint;
import android.os.AsyncTask;
import android.util.Log;
import android.widget.TextView;
import android.os.Bundle;

import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.PreparedStatement;
import java.sql.ResultSet;
import java.util.HashMap;
import java.util.Map;

public class MainActivity extends AppCompatActivity {
    private static final String URL = "jdbc:mysql://";
    private static final String USER = "kodejava";
    private static final String PASSWORD = "kodejava";

    protected void onCreate(Bundle savedInstanceState) {

        new InfoAsyncTask().execute();

    public class InfoAsyncTask extends AsyncTask<Void, Void, Map<String, String>> {
        protected Map<String, String> doInBackground(Void... voids) {
            Map<String, String> info = new HashMap<>();

            try (Connection connection = DriverManager.getConnection(URL, USER, PASSWORD)) {
                String sql = "SELECT name, address, phone_number FROM school_info LIMIT 1";
                PreparedStatement statement = connection.prepareStatement(sql);
                ResultSet resultSet = statement.executeQuery();
                if ( {
                    info.put("name", resultSet.getString("name"));
                    info.put("address", resultSet.getString("address"));
                    info.put("phone_number", resultSet.getString("phone_number"));
            } catch (Exception e) {
                Log.e("InfoAsyncTask", "Error reading school information", e);

            return info;

        protected void onPostExecute(Map<String, String> result) {
            if (!result.isEmpty()) {
                TextView textViewName = findViewById(;
                TextView textViewAddress = findViewById(;
                TextView textViewPhoneNumber = findViewById(;

  • Finally, here is the screenshot of our Android application.
Android - MySQL JDBC

Android – MySQL JDBC

The complete source code can be accesses in our GitHub repository here: android-mysql-example.

How to Create a Database in MySQL


When you build up an application, you need a database (db) to save your data. It could be about your order, member, or transactional data. It really depends on business needs from the application that you build. Another purpose is you can initiate improvements based on huge data that you’ve already saved.

Based on Wikipedia, a database is an organized collection of data, generally stored and accessed electronically from a computer system. Where databases are more complex they are often developed using formal design and modeling techniques Wikipedia.

There are many great databases these days, one of it is MySQL. In this section, we will learn from the beginning how to create a database, tables, and query data with MySQL.

Why MySQL:

  • It is open source. However, there are a personal and enterprise version.
  • Fast. Of course with the right indexes when you have huge amount of rows data.
  • Scalability, maintainability.
  • Suitable for web-based application. E-commerce, warehouse, logging, and many more.

Before we start, to create or manage your MySQL database, you need database client/IDE.

Three IDE options:

Personally, I find Sequel Pro is very helpful and powerful for my day-to-day use.

Start and Login to MySQL on your local machine (Mac OS X).

  1. Go to your System Preferences
  2. Find MySQL
  3. Choose to Start MySQL Server

After the MySQL database started, you can log in.

  1. Go to your database client, in this example I am using Sequel Pro.
  2. Connect to your localhost. You need to provide the username and password before login.
  3. Once you connect, you will be able to create your database.

Create new Database:

Create Database Statements
CREATE DATABASE database_name
    [[DEFAULT] CHARACTER SET charset_name]
    [[DEFAULT] COLLATE collation_name];


CREATE DATABASE learning_mysql 
    COLLATE utf8_general_ci;

Using Functionality Provided by IDE
  • Go to Database menu, select Add Database…

  • Then fill in the database name

For common cases and non latin, use UTF-8 for character set, and you can use utf8_general_ci for the collation.

Your database is now ready to use. Ensure you choose the right database that you want to manage. The second step is to prepare tables as per your business needs, to save the data from your application.

Happy exploring!

How do I backup MySQL databases in Ubuntu?

What is MySQL

MySQL is an open-source RDBMS (Relational Database Management System). As the name implied it uses SQL (Structured Query Language) to access and manipulate data. MySQL has been widely used to store and manage data ranging from a simple web application to an enterprise class application.

The importance of data in every application require us to regularly back up the data to prevent data loss, for example caused by hardware crashes. In this post I will show you how to back up the database manually and using a script combined with a cron job to run the process automatically.

Using mysqldump

To create a database backup in MySQL we can use the mysqldump command. The example syntax of using this command is:

mysqldump -u username -p database_to_backup > backup_file_name.sql

If you need to restore the database you can use the following command:

mysql -u username -p database_to_restore < backup_file_name.sql

Before you can execute the command you might need to create the database if you don’t already have it.

saturn@ubuntu:~$ mysql -u root -p
CREATE DATABASE database_to_restore;

Creating Backup Script

To start let’s create MySQL user account that we are going to use to do the backup process. Login to MySQL using mysql -u root -p command. Type and execute the following command to create backupuser.

grant lock tables, select, show view on kodejava.* to 'backupuser'@'localhost' identified by 'backuppasswd';
flush privileges;

Exit from the MySQL using the exit command and create the following backup script called using your favorite editor. For example, you can use nano or vim to create the file.


directory="$(date +%Y%m%d)"

if [ ! -d "$directory" ]; then
    mkdir $directory

backup="kodejava-$(date +%Y%m%d%H%M%S)"

mysqldump -ubackupuser -pbackuppasswd --opt kodejava > $backupdir/$backup.sql

cd $directory
tar -czf $backup.tar.gz $backup.sql
rm $backup.sql

To make the file executable you need to run the chmod +x command.

Creating Scheduler Using Crontab

The crontab command is used to schedule commands to be executed periodically at a predetermined time. It will run as a background process without needing user intervention. These kinds of jobs are generally referred to as cron jobs and the jobs will run as the user who creates the cron jobs.

In the example below we register a cron job to execute the script at 12:00AM every day. To edit the cron jobs type crontab -e, this will open the crontab file.

saturn@ubuntu:~$ crontab -e
no crontab for saturn - using an empty one

Select an editor.  To change later, run 'select-editor'.
  1. /bin/ed
  2. /bin/nano        <---- easiest
  3. /usr/bin/vim.basic
  4. /usr/bin/vim.tiny

Choose 1-4 [2]:

Select an editor to edit the crontab, choose by entering the number of the editor. The easiest one is nano but you can also use vim if you comfortable with it.

And you will see an empty crontab file will the following commented messages:

# Edit this file to introduce tasks to be run by cron.
# Each task to run has to be defined through a single line
# indicating with different fields when the task will be run
# and what command to run for the task
# To define the time you can provide concrete values for
# minute (m), hour (h), day of month (dom), month (mon),
# and day of week (dow) or use '*' in these fields (for 'any').#
# Notice that tasks will be started based on the cron's system
# daemon's notion of time and timezones.
# Output of the crontab jobs (including errors) is sent through
# email to the user the crontab file belongs to (unless redirected).
# For example, you can run a backup of all your user accounts
# at 5 a.m every week with:
# 0 5 * * 1 tar -zcf /var/backups/home.tgz /home/
# For more information see the manual pages of crontab(5) and cron(8)
# m h  dom mon dow   command

Go to the end of the file and write the following entry to register a cron job. In the example below we register a cron job to execute the script at 12:00M every day.

# m h  dom mon dow   command
  0 0   *   *   *    /home/saturn/

After you save the file you can use the crontab -l command to list the registered cron job. If you want to know more about crontab you can visit crontab guru website.

How to create a read-only MySQL user?


There are times when you need to create a user only to have read-only access to a database. The user can view or read the data in the database, but they cannot make any changes to the data or the database structure.

Creating a New User Account

To create a read-only database user account for MySQL do the following steps:

  • First, login as a MySQL administrator from your terminal / command prompt using the following command:
mysql -u root -p
  • You’ll be prompted to enter the password. Type the password for the root account.
  • Create a new MySQL user account.
CREATE USER 'report'@'%' IDENTIFIED BY 'secret';

The % in the command above means that user report can be used to connect from any host. You can limit the access by defining the host from where the user can connect. Omitting this information will only allow the user to connect from the same machine.

  • Grant the SELECT privilege to user.
GRANT SELECT ON kodejava.* TO 'report'@'%';
  • Execute the following command to make the privilege changes saved and take effect.
  • Type quit to exit from the MySQL shell.

Test the New User Account

  • Now we can try the newly created user account. Start by login with the new user account and provide the corresponding password.
mysql -u report -p
  • Try executing the DELETE command:
mysql> USE kodejava;
Reading table information for completion of table and column names
You can turn off this feature to get a quicker startup with -A

Database changed
mysql> DELETE FROM authors;
ERROR 1142 (42000): DELETE command denied to user 'report'@'localhost' for table 'authors'
mysql> UPDATE authors SET name = 'Wayan Saryada' WHERE id = 1;
ERROR 1142 (42000): UPDATE command denied to user 'report'@'localhost' for table 'authors'