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🗣 Wd提问: ruby mysql

🤖 Ai回答:
To work with MySQL in Ruby, you typically use the `mysql2` gem — which is the modern, recommended gem for connecting to MySQL databases from Ruby applications (especially for Rails and non-Rails projects).

✅ Step-by-Step: Using MySQL in Ruby

1、Add the Gem to Your Project

If you're using Bundler (Rails or non-Rails), add this to your `Gemfile`:

ruby
gem 'mysql2'

Then run:

bash
bundle install

⚠️ Note: If you’re on macOS and have issues installing `mysql2`, you might need to install MySQL via Homebrew first:

bash
brew install mysql@8.0

And then set the `MYSQL2_LIB_DIR` and `MYSQL2_INCLUDE_DIR` if needed.

2、Basic Connection Example

Here’s a simple Ruby script that connects to MySQL and runs a query:

ruby
require 'mysql2'

Connect to MySQL
client = Mysql2::Client.new(
host: 'localhost',
username: 'your_username',
password: 'your_password',
database: 'your_database_name',
port: 3306
)

Execute a query
results = client.query(SELECT * FROM users)

Print results
results.each do |row|
puts row
end

Close connection
client.close

💡 You can also use `begin...rescue...end` blocks for error handling.

3、Using Prepared Statements (Safe from SQL Injection)

ruby
client = Mysql2::Client.new(...)

Use prepared statement
stmt = client.prepare(SELECT name FROM users WHERE id = ?)
result = stmt.execute(5)

result.each do |row|
puts row['name']
end

stmt.close

4、Error Handling

ruby
begin
client = Mysql2::Client.new(...)
result = client.query(SELECT * FROM non_existent_table)
rescue Mysql2::Error = e
puts Database error: {e.message}
ensure
client&.close
end

5、With ActiveRecord (if using Rails)

If you’re in a Rails app, you don’t need to manually connect — Rails configures it automatically via `config/database.yml`.

Example `database.yml`:

yaml
development:
adapter: mysql2
encoding: utf8mb4
pool: 5
username: root
password:
host: localhost
database: myapp_development

Then just define models and use them:

ruby
User.all
User.find(1)
User.create(name: John)

6、Install MySQL Server (if not installed)

On Ubuntu/Debian:

bash
sudo apt update
sudo apt install mysql-server
sudo systemctl start mysql
sudo mysql_secure_installation

On macOS (Homebrew):

bash
brew install mysql
brew services start mysql

7、Check Connection Works

You can test your connection with a simple Ruby script:

ruby
require 'mysql2'

begin
client = Mysql2::Client.new(
host: 'localhost',
username: 'root',
password: '',
database: 'test_db'
)
puts Connected successfully!
client.close
rescue = e
puts Failed: {e.message}
end

📌 Best Practices

Always use prepared statements to avoid SQL injection.
Never hardcode passwords — use environment variables (`ENV['DB_PASSWORD']`).
Use connection pooling in production apps (e.g., via `connection_pool` gem).
Consider using `ActiveRecord` if you’re building a web app (Rails or otherwise).

🧩 Alternative: `pg` for PostgreSQL

If you ever need to switch to PostgreSQL, use `pg` gem instead:

ruby
gem 'pg'

But for MySQL → stick with `mysql2`.

📚 Resources

[mysql2 GitHub](https://github.com/brianmario/mysql2)
[Mysql2 Docs](https://www.rubydoc.info/gems/mysql2/)
[Ruby on Rails Database Configuration](https://guides.rubyonrails.org/configuring.htmlconfiguring-a-database)

Let me know if you want help setting up a full Rails app with MySQL, or connecting to a remote database, or writing migrations! 😊

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