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Вопрос		Ответ
Ensures that a column cannot have a NULL value начать обучение		NOT NULL
Ensures that all values in a column are different начать обучение		UNIQUE
A combination of a NOT NULL and UNIQUE. Uniquely identifies each row in a table начать обучение		PRIMARY KEY [MySQL:] UserId auto_increment primary key
Uniquely identifies a row/record in another table начать обучение		FOREIGN KEY
Ensures that all values in a column satisfies a specific condition начать обучение		CHECK
Sets a default value for a column when no value is specified начать обучение		DEFAULT
Used to create and retrieve data from the database very quickly начать обучение		INDEX
It's like a declaration of default value that increments by 1 for each record. начать обучение		auto_increment SQLite: autoincrement

SQL – Constraints