Learning SQL
Complete SQL course with guided lessons, challenges, integrated IDE and completion certificate. Learn databases and queries for exams, IT and dev career.
A class should have only one reason to change. Each class must have a single responsibility.
Entities should be open for extension, but closed for modification.
Objects of a superclass should be replaceable with objects of their subclasses without breaking the application.
Clients should not be forced to depend on interfaces they don't use. Prefer specific interfaces.
Depend on abstractions, not concrete implementations. High-level modules should not depend on low-level modules.
Complete SQL course with guided lessons, challenges, integrated IDE and completion certificate. Learn databases and queries for exams, IT and dev career.
Complete SQL course with guided lessons, challenges, integrated IDE and completion certificate. Learn databases and queries for exams, IT and dev career.
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