Sequel is a simple, flexible, and powerful SQL database access toolkit for Ruby. Sequel provides thread safety, connection pooling, and a concise DSL for constructing SQL queries and table schemas. Sequel includes a comprehensive ORM layer for mapping records to Ruby objects and handling associated records. Sequel supports advanced database features such as prepared statements, bound variables, savepoints, two-phase commit, transaction isolation, primary/replica configurations, and database sharding. Sequel currently has adapters for ADO, Amalgalite, IBM_DB, JDBC, MySQL, Mysql2, ODBC, Oracle, PostgreSQL, SQLAnywhere, SQLite3, TinyTDS, and Trilogy.
Summary
Sequel is a robust SQL database access toolkit for Ruby, designed to simplify and streamline database interactions. It offers a comprehensive ORM layer that maps records to Ruby objects and handles associated records. Sequel is known for its thread safety, connection pooling, and a concise DSL for constructing SQL queries and table schemas. It supports a wide range of advanced database features, including prepared statements, bound variables, savepoints, two-phase commit, transaction isolation, primary/replica configurations, and database sharding.
Sequel is compatible with various database adapters such as ADO, Amalgalite, IBM_DB, JDBC, MySQL, Mysql2, ODBC, Oracle, PostgreSQL, SQLAnywhere, SQLite3, TinyTDS, and Trilogy. This extensive compatibility makes it a versatile choice for developers working with different database systems.
Getting Started
Connecting to a Database
To connect to a database, you simply provide `Sequel.connect` with a URL. The connection URL can include the username, password, and port. Optional parameters like connection pool size and loggers for logging SQL queries can also be specified. Alternatively, you can use a hash instead of a connection URL, but ensure to include the `:adapter` option.
```ruby
DB = Sequel.connect('postgres://user:password@localhost/mydb')
Retrieving Records
Sequel uses the concept of datasets to retrieve data. A Dataset object encapsulates an SQL query and supports chainability, letting you fetch data using a convenient Ruby DSL. For instance, you can retrieve all records using the `all` method, which returns an array of hashes, each corresponding to a record.
```ruby
DB[:items].all
Filtering Records
Filtering records is straightforward. You can provide a hash of values to match using the `where` method. Sequel also supports filtering via ranges, arrays of values, and even regular expressions for databases like PostgreSQL and MySQL.
```ruby
DB[:items].where(category: 'books').all
Inserting, Updating, and Deleting Records
Inserting records into the table is done with the `insert` method. Updating records uses the `update` method, and deleting records is done with the `delete` method. It is crucial to use the `where` method first to specify the records you want to update or delete.
```ruby
DB[:items].insert(name: 'New Book', category: 'books')
DB[:items].where(id: 1).update(name: 'Updated Book')
DB[:items].where(id: 1).delete
Advanced Features
Transactions
Sequel allows you to wrap a block of code in a database transaction using the `Database#transaction` method. If the block does not raise an exception, the transaction will be committed. Otherwise, it will be rolled back.
```ruby
DB.transaction do
DB[:items].insert(name: 'New Book')
raise Sequel::Rollback
end
Associations and Eager Loading
Sequel supports associations to specify relationships between model classes, reflecting relationships between tables in the database. Associations can be eagerly loaded to optimize queries by loading all associated objects for all current objects in one query.
```ruby
class Book < Sequel::Model
many_to_one :author
end
books = Book.eager(:author).all
Security
Designing applications with security in mind is a best practice. Sequel provides a Security Guide detailing security issues you should be aware of when using the toolkit. This includes preventing SQL injection and ensuring data integrity.
Conclusion
Sequel is a powerful and flexible toolkit for Ruby developers, offering a comprehensive set of features for database interaction. Its ease of use, combined with advanced capabilities, makes it an excellent choice for both simple and complex applications.
Image: Sequel Database Toolkit for Ruby
Remember these 3 key ideas for your startup:
Simplified Database Management: Sequel takes away the hassle of connecting to databases and manipulating them, allowing you to focus on your application logic. This can significantly reduce development time and complexity.
Advanced Features: With support for advanced database features like prepared statements, transaction isolation, and database sharding, Sequel ensures your application can scale and handle complex database operations efficiently.
Security and Flexibility: Sequel's design prioritizes security and flexibility, making it easier to build secure applications. Its comprehensive ORM layer and support for various database adapters make it a versatile choice for startups and SMEs.
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