Relational Databases

(a)

Both Assertion and Reason are true and Reason is the correct explanation of Assertion.

Explanation
A database may be defined as a collection of interrelated data stored together (centrally) to serve multiple applications. A DBMS (Data Base Management System) refers to a software that is responsible for storing, maintaining and utilizing databases. A database along with a DBMS is referred to as a database system.

(a)

Both Assertion and Reason are true and Reason is the correct explanation of Assertion.

Explanation
Data redundancy refers to the duplication of data in a database. This may lead to data inconsistency. When redundant data or the multiple copies of data mismatch, it makes the data inconsistent.

(c)

Assertion is true but Reason is false.

Explanation
Data redundancy may lead to many problems. It refers to the duplication of data in a database, which can result in data inconsistencies, increased storage requirements, and difficulties in maintaining data integrity. In RDBMS, data redundancy is minimized but not completely eliminated.

(a)

Both Assertion and Reason are true and Reason is the correct explanation of Assertion.

Explanation
A primary key is used to uniquely identify the rows in a data table. It is a set of one or more attributes that can uniquely identify tuples (rows) within the relation.

(c)

Assertion is true but Reason is false.

Explanation
A data table can have only one primary key. There can be more than one attribute in a relation possessing the unique identification property. They are known as candidate keys.

(a)

Both Assertion and Reason are true and Reason is the correct explanation of Assertion.

Explanation
There can be more than one attribute in a relation possessing the unique identification property. All attribute combinations inside a relation that can serve as a primary key are candidate keys, as they are candidates for the primary key position.

(d)

Assertion is false but Reason is true.

Explanation
Not all types of keys necessarily contain unique values for each row. While primary keys ensure uniqueness for each row in a table, other types of keys, such as foreign keys and candidate keys, may not guarantee uniqueness. A non-key attribute, whose values are derived from the primary key of some other table, is known as foreign key in its current table.

(a)

Both Assertion and Reason are true and Reason is the correct explanation of Assertion.

Explanation
The foreign keys of tables are utilized to establish relationships with other tables, while referential integrity is a system of rules that a DBMS employs to ensure the validity of relationships between records in related tables. This system prevents users from accidentally deleting or changing related data. Therefore, it is crucial to handle foreign keys carefully.

(c)

Assertion is true but Reason is false.

Explanation
A primary key is a set of one or more attributes (columns) that can uniquely identify tuples within the relation. When a primary key is made up of two or more attributes, it is called as composite primary key. Hence, the reason is false.

A database is defined as a collection of interrelated data stored together to serve multiple applications.

The Structured Query Language (SQL) is a language that enables us to create and operate on relational databases (RDBMS), which are sets of related information stored in tables.

A view is a (virtual) table that does not really exist in its own right but is instead derived from one or more underlying base tables.

Duplication of data is known as data redundancy. Data redundancy in a database leads to wasted storage and multiple copies of the same data. When these copies do not match with one another, it leads to data inconsistency. Additionally, data redundancy can result in performance degradation, security risks, and increased complexity.

Mismatched multiple copies of same data is known as data inconsistency. Data inconsistency undermines database reliability, hindering decision-making, causing operational errors, and increasing complexity.

The rows of tables (relations) are called tuples.

The columns of tables (relations) are called attributes.

A domain is a pool of values from which the actual values appearing in a given column are drawn.

The number of attributes in a relation is called degree of a relation.

The number of rows in a relation is known as cardinality of the relation.

A primary key is a set of one or more attributes that can uniquely identify tuples within the relation.

A non-key attribute, whose values are derived from the primary key of some other table, is known as foreign key in its current table.

MySQL is a freely available open source Relational Database Management System (RDBMS) that uses Structured Query Language (SQL). MySQL provides us with a rich set of features that support a secure environment for storing, maintaining and accessing data.

The functions and features of MySQL are as follows :

1. Speed — If the server hardware is optimal, MySQL runs very fast. It supports clustered servers for demanding applications.
2. Ease of use — MySQL is a high performance, relatively simple database system. From the beginning, MySQL has typically been configured, monitored and managed from the command line. However, several MySQL graphical interfaces are also available.
3. Query Language Support — MySQL understands standards based SQL.
4. Portability — MySQL provides portability as it has been tested with a broad range of different compilers and can work on many different platforms. It is fully multi-threaded using kernel threads. It can easily use multiple CPUs if they are available.
5. Cost — MySQL is available free of cost. MySQL is a open source database.
6. Data Types — MySQL provides many data types to support different types of data. It also supports fixed-length and variable-length records.
7. Security — MySQL offers a privilege and password system that is very flexible and secure, and that allows host-based verification. Passwords are secure because all password traffic is encrypted when we connect to a server.
8. Scalability and Limits — MySQL can handle large databases. Some real life MySQL databases contain 50 million records, some have up to 60,000 tables and about 5,000,000,000 rows.
9. Connectivity — Clients can connect to MySQL Server using several protocols.
10. Localization — The server can provide error messages to clients in many languages.
11. Clients and Tools — MySQL provides several client and utility programs. These include both command-line programs such as mysqldump and mysqladmin, and graphical programs such as MySQL Administrator and MySQL Query Browser. MySQL Server has built-in support for SQL statements to check, optimize and repair tables.

A database server is the key to solving the problems of database management system (information system). In general, a server must reliably manage a large amount of data in a multi-user environment so that many users can concurrently access the same data. A database server must also prevent unauthorized access and provide efficient solutions for failure recovery.

The key features of MySQL are as follows :

1. Speed — If the server hardware is optimal, MySQL runs very fast. It supports clustered servers for demanding applications.
2. Ease of use — MySQL is a high performance, relatively simple database system. From the beginning, MySQL has typically been configured, monitored and managed from the command line. However, several MySQL graphical interfaces are also available.
3. Query Language Support — MySQL understands standards based SQL.
4. Portability — MySQL provides portability as it has been tested with a broad range of different compilers and can work on many different platforms. It is fully multi-threaded using kernel threads. It can easily use multiple CPUs if they are available.
5. Cost — MySQL is available free of cost. MySQL is a open source database.
6. Data Types — MySQL provides many data types to support different types of data. It also supports fixed-length and variable-length records.
7. Security — MySQL offers a privilege and password system that is very flexible and secure, and that allows host-based verification. Passwords are secure because all password traffic is encrypted when we connect to a server.
8. Scalability and Limits — MySQL can handle large databases. Some real life MySQL databases contain 50 million records, some have up to 60,000 tables and about 5,000,000,000 rows.
9. Connectivity — Clients can connect to MySQL Server using several protocols.
10. Localization — The server can provide error messages to clients in many languages.
11. Clients and Tools — MySQL provides several client and utility programs. These include both command-line programs such as mysqldump and mysqladmin, and graphical programs such as MySQL Administrator and MySQL Query Browser. MySQL Server has built-in support for SQL statements to check, optimize and repair tables.

All programs and users accessing data within the MySQL database must utilize Structured Query Language (SQL). MySQL is compatible with standard-based SQL, enabling it to understand and process SQL commands efficiently. Additionally, the MySQL server incorporates built-in support for executing SQL statements, allowing users to perform tasks such as checking, optimizing, and repairing tables.

SQL commands can be divided into the following categories :

1. Data Definition Language (DDL) Commands
2. Data Manipulation Language (DML) Commands
3. Transaction Control Language (TCL) Commands
4. Session Control Commands
5. System Control Commands

An ideal DDL should perform the following functions :

1. It should identify the types of data division such as data item, segment, record and data-base file.
2. It should give a unique name to each data-item-type, record-type, file-type, database and other data subdivision.
3. It should specify the proper data types.
4. It should specify how the record types are related to make structures.
5. It may define the type of encoding the program uses in the data items (binary, character, bit, string etc.). This should not be confused with the encoding employed in physical representation.
6. It may define the length of the data items.
7. It may define the range of values that a data-item can assume.
8. It may specify means of checking for errors in the data.
9. It may specify privacy locks for preventing unauthorized reading or modification of the data.
10. A logical data definition should not specify addressing, indexing or searching techniques or specify the placement of data on the storage units, because these topics are in the domain of physical, not logical, organization.

Commands used to assign/revoke privileges from database users are GRANT, REVOKE.

Table maintenance commands are ANALYZE TABLE, CHECK TABLE, REPAIR TABLE, RESTORE TABLE.

TCL part of SQL includes commands for specifying the beginning and ending of transactions along with commands to have control over transaction processing. Some examples of TCL commands are COMMIT, ROLLBACK, SET TRANSACTION and SAVEPOINT. These commands manage changes made by DML commands.

A relation is a table i.e., data arranged in rows and columns.

The rows of tables (relations) are called tuples.

The columns of tables (relations) are called attributes.

A domain is a pool of values from which the actual values appearing in a given column are drawn.

A primary key is a set of one or more attributes that can uniquely identify tuples within the relation.

All attribute combinations inside a relation that can serve as primary key are candidate keys as they are candidates for the primary key position.

The cartesian product is an operation that combines every row of one table with every row of another table to create a new table.

The number of attributes in a relation is called degree of a relation.

A view is a (virtual) table that does not really exist in its own right but is instead derived from one or more underlying base tables. Views are useful to view desired information that is actually stored in a base table and they extend the control we have over our data. They are an excellent way to give people access to some but not all of the information in a table.

A primary key is a set of one or more attributes that can uniquely identify tuples within the relation.

All attribute combinations inside a relation that can serve as primary key are candidate keys as they are candidates for the primary key position.

A candidate key that is not the primary key is called an alternate key.

A non-key attribute, whose values are derived from the primary key of some other table, is known as foreign key in its current table.

A candidate key that is not the primary key is called an alternate key.

The importance of a Primary Key in a table lies in its ability to uniquely identify tuples (or rows) within the table.

In this table, the "Salesman Number" column can be designated as the primary key. Each "Salesman Number" value uniquely identifies a salesperson in the table, and no two salespersons can have the same number. Additionally, the "Salesman Number" column would not accept null values, ensuring that every salesperson has a valid identifier.

A primary key is a set of one or more attributes that can uniquely identify tuples within the relation. The primary key is non-redundant, meaning it does not have duplicate values in the same relation, and non-null attribute, meaning a null value cannot be inserted into it.

The number of attributes in a relation is called Degree of a relation. A relation having 3 attributes is said to be a relation of degree 3. Similarly, a relation having n attributes is said to be a relation of degree n.

All attribute combinations inside a relation that can serve as primary key are candidate keys as they are candidates for the primary key position.

The number of rows in a relation is known as cardinality of the relation.

Tables

Reason — A relational database consists of a collection of tables, which are used to organize and store data. Each table consists of rows and columns, where rows represent individual records or tuples, and columns represent attributes or fields.

Relations

Reason — A relational database consists of a collection of tables, which are used to organize and store data. These tables are called relations. Each table consists of rows and columns, where rows represent individual records or tuples, and columns represent attributes or fields.

Tuple

Reason — A tuple (rows) in a table represents a logical relationship among a set of values.

Tuple

Reason — Tuple (Rows) of the table is used to refer to a record in a table.

Attribute

Reason — Attribute (columns) of the table is used to refer to a field in a table.

Key

Reason — Within the given relation, a set of one or more attributes having values that are unique within the relation and thus are able to uniquely identify that tuple, is said to be key of the relation.

Street

Reason — Attributes "Id," "License number," and "Dept_id" are unique identifiers and can be suitable choices for a primary key. However, "Street" might not be unique for each tuple, as multiple tuples could have the same street value, making it unsuitable for a primary key.

Primary

Reason — A non-key attribute, whose values are derived from the primary key of some other table, is known as foreign key in its current table.

ID

Reason — The "ID" attribute serves as a unique identifier for each student, making it suitable for use as a primary key.

QAL

Reason — A legal sub-language of SQL includes DDL (Data Definition Language), DML (Data Manipulation Language), and TCL (Transaction Control Language).

True

Reason — In a relational database, a table can store empty values, represented as NULL.

False

Reason — A relation is a table having ordered atomic values.

False

Reason — A primary key is non-null, meaning a null value cannot be inserted into it because such values would violate the uniqueness constraint required by the primary key.

False

Reason — A common attribute between two tables is not necessarily called a foreign key. Instead, a non-key attribute, whose values are derived from the primary key of some other table, is known as foreign key in its current table. A foreign key is used to represent the relationship between two tables.

True

Reason — A non-key attribute, whose values are derived from the primary key of some other table, is known as a foreign key in its current table.

True

Reason — DDL (Data Definition Language) commands are used to create and define tables and other database objects in SQL (Structured Query Language). DDL commands such as CREATE, ALTER, and DROP, are used to create, define, change and delete objects like tables, indexes, views, and constraints.

False

Reason — Part of SQL which manipulates data in tables, is called DML.

True

Reason — A Data Manipulation Language (DML) is a language that enables users to access or manipulate data as organized by the appropriate data model. Hence, part of SQL which accesses and manipulates data in tables, is called DML. These commands include SELECT, LOCK TABLE, UPDATE, INSERT INTO, DELETE.

True

Reason — Transaction Control Language (TCL) commands in SQL are used to manage and control transactions. These commands include COMMIT, ROLLBACK, SET TRANSACTION and SAVEPOINT.

False

Reason — MySQL is a freely available open source Relational Database Management System (RDBMS) that uses Structured Query Language (SQL).