Connect to OceanBase Database by using Sequel

This topic introduces how to build an application by using Sequel and OceanBase Database and perform basic database operations, including table creation, data insertion, data updating, and data querying.

Prerequisites

• You have installed Ruby and RubyGems.
• You have installed OceanBase Database and created a MySQL-compatible tenant.

Procedure

1. Check the versions of Ruby and RubyGems.
2. Install the necessary gems.
3. Obtain the connection information of OceanBase Database.
4. Create a sample application.
5. Run the sample application.

Step 1: Check the versions of Ruby and RubyGems

Open the terminal and run the following command to check the versions of Ruby and RubyGems:

ruby -v
gem -v

Step 2: Install the necessary gems

Run the following command to install Sequel and mysql2:

gem install sequel mysql2

Step 3: Obtain the connection information of OceanBase Database

Contact the deployment personnel or administrator of OceanBase Database to obtain the database connection string.

mysql -h$host -P$port -u$user_name -p$password -D$database_name

Parameter description:

• $host: the IP address for connecting to OceanBase Database.
• $port: the port for connecting to OceanBase Database.
• $database_name: the name of the database to be accessed.
• $user_name: the tenant account.
• $password: the password of the account.

Step 4: Create an example program

1. Create a configuration file named config.rb:

   PASSWORD = ENV['OB_PASSWORD'] || 'your_password'
   
   CLIENT_CONFIG = {
     adapter: 'mysql2',
     host: 'your_host',
     port: your_port,
     username: 'your_username',
     password: PASSWORD,
     all_databases: true
   }
   

2. Create an example program named main.rb:

   require 'sequel'
   require 'sequel/adapters/mysql2'
   require File.expand_path('config.rb', __dir__)
   
   # Create a connection.
   db = Sequel.connect(CLIENT_CONFIG)
   
   # Create a database.
   db_name = "ruby_test_db"
   db.run("CREATE DATABASE IF NOT EXISTS #{db_name}")
   
   db.disconnect
   
   # Reconnect to the new database.
   CLIENT_CONFIG[:database] = db_name
   db = Sequel.connect(CLIENT_CONFIG)
   puts "Database '#{db_name}' selected"
   
   # Create a table.
   db.run("DROP TABLE IF EXISTS users")
   db.run("CREATE TABLE users (
     id INT AUTO_INCREMENT PRIMARY KEY,
     name VARCHAR(255) NOT NULL,
     created_at TIMESTAMP DEFAULT CURRENT_TIMESTAMP
   )")
   
   # Insert sample data.
   sample_names = ["Alice", "Bob", "Charlie", "David"]
   sample_names.each do |name|
     db.run("INSERT INTO users (name) VALUES ('#{name}')")
   end
   
   puts "Table created and sample data inserted successfully"
   puts "Inserted #{sample_names.size} sample records"
   
   # Query and display all data.
   results = db[:users]
   puts "\nUsers:"
   results.each do |row|
     puts "ID: #{row[:id]}, Name: #{row[:name]}, Created at: #{row[:created_at]}"
   end
   
   # Close the connection.
   db.disconnect
   

Step 5: Run the example program

1. Run the following command:

   ruby main.rb
   

   Expected result:

   Database 'ruby_test_db' selected
   Table created and sample data inserted successfully
   Inserted 4 sample records
   
   Users:
   ID: 1, Name: Alice, Created at: 2025-05-21 15:20:06 +0800
   ID: 2, Name: Bob, Created at: 2025-05-21 15:20:06 +0800
   ID: 3, Name: Charlie, Created at: 2025-05-21 15:20:06 +0800
   ID: 4, Name: David, Created at: 2025-05-21 15:20:06 +0800
   

FAQ

1. Connection error: If you cannot connect to the database, check the following items:

   • Whether the database address and port are correct
   • Whether the username and password are correct
   • Whether the network connection is normal

2. Privilege error: If you encounter a privilege-related error, make sure that the user has sufficient privileges to perform the required operation.

3. SQL syntax error: If there is a syntax error in the SQL statement, check whether the syntax is correct.

Performance optimization suggestions

1. Use batch operations of Sequel.
2. Use a connection pool to manage database connections.
3. Use precompiled queries.
4. Use caching properly.
5. Optimize database indexes.