Question Answer We cannot update the schema after the creation of a database. A relational schema describes the data that is contained in a relational instance. The relational algebra operates on a single tuple. Every Join operation can be expressed as a combination of cross products and other basic operations. The SQL allows NULL on any attributes. The “group by" operation is used to generate ordered data. In the same database, two attributes cannot have the same name. We should set as much default constraints as possible to ensure the correctness of a table. A table can have, at most, two foreign keys. By default, the results of a SQL query are the unique values without duplicates.

Question Answer We cannot update the schema after the creation of a database. A relational schema describes the data that is contained in a relational instance. The relational algebra operates on a single tuple. Every Join operation can be expressed as a combination of cross products and other basic operations. The SQL allows NULL on any attributes. The “group by" operation is used to generate ordered data. In the same database, two attributes cannot have the same name. We should set as much default constraints as possible to ensure the correctness of a table. A table can have, at most, two foreign keys. By default, the results of a SQL query are the unique values without duplicates.

Database System Concepts

7th Edition

ISBN:9780078022159

Author:Abraham Silberschatz Professor, Henry F. Korth, S. Sudarshan

Publisher:Abraham Silberschatz Professor, Henry F. Korth, S. Sudarshan

Chapter1: Introduction

Section: Chapter Questions

Problem 1PE

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