Query Maestro - Round 1(Set 2)

Entities are the objects or concepts that we want to store information about in a database. They have properties called attributes that describe the characteristics of the entity. Therefore, attributes are the properties of entities. The other options, such as groups, table, and switchboards, are not directly related to the properties of entities in a database context.

A relationship between two entities is called a binary relationship. In a binary relationship, there are two entities involved, and they are connected or related to each other in some way. This type of relationship is commonly seen in databases, where two tables are linked through a common attribute. For example, in a database of students and courses, the binary relationship would be established between a student and the course they are enrolled in.

DDL (Data Definition Language) is used to define the structure and organization of the database, including creating tables, defining relationships, and setting constraints. DML (Data Manipulation Language) is used to manipulate the data within the database, such as inserting, updating, and deleting records. Therefore, using DDL and DML together, it is possible to completely define a schema by creating the necessary tables and defining their attributes, as well as manipulating the data within those tables. VDL and SDL are not commonly used terms in database management, so they are not relevant to defining a schema.

Relational Algebra is a procedural query language used for manipulating and querying relational databases. It provides a set of operations that can be used to retrieve specific data from a database, such as selection, projection, join, and union. These operations are performed step by step, in a procedural manner, to obtain the desired result. Therefore, the correct answer is "Procedural query Language".

A hashed file organization uses a hash function to generate a unique address for each record in the file. This allows for direct access to any record in the file, resulting in very fast access times. Unlike an ordered file that requires sequential searching or a B-tree that requires tree traversal, a hashed file provides the most efficient access to arbitrary records. An unordered file does not provide any specific organization or indexing, making it less efficient for accessing specific records. Therefore, a hashed file is the correct answer as it offers the fastest access to any arbitrary record in a file.

A view is a virtual table that does not physically exist in the database. It is a saved SQL query that can be treated as a table and used in other queries. When a query is executed on a view, the underlying data is retrieved from the base tables. Views provide a way to simplify complex queries, restrict access to certain data, and present data in a customized format without actually storing the data separately. Therefore, a view is the correct answer as it does not have a physical existence in the database.

Conceptual design involves creating a high-level model of the database system that is independent of any specific database management system (DBMS). This means that the design focuses on the overall structure and organization of the database, rather than the specific implementation details of a particular DBMS. Therefore, the statement "Conceptual design involves modelling independent of the DBMS" is true.

The conceptual view refers to the overall logical organization and structure of the entire database. It provides a high-level perspective of the data, focusing on the relationships between different entities and the rules governing them. This view is independent of any specific implementation or physical storage details. It allows users to understand and interact with the database at a conceptual level, without needing to know the underlying technical aspects.

The correct answer is "Alter". In SQL, the "Alter" statement is used to modify the structure or definition of a table. It allows you to add, modify, or delete columns, constraints, indexes, and other table attributes. The "Alter" statement is commonly used to make changes to an existing table without having to recreate it.

The statement "SELECT * FROM employee" is a DML (Data Manipulation Language) statement. DML statements are used to retrieve, manipulate, and manage data in a database. In this case, the SELECT statement is used to retrieve all columns and rows from the "employee" table. It does not make any changes to the data, but it is still considered a DML statement because it is part of the language used to manipulate data in a database.

The Cartesian product in relational algebra is a binary operator because it takes two relations as input and produces a new relation as output. It combines every row from the first relation with every row from the second relation, resulting in a new relation with all possible combinations of rows from the two input relations.

The relational model offers much more data independence compared to other database models. This means that the data is stored separately from the applications that use it, allowing for easier modifications and updates without affecting the entire system. This independence also allows for better scalability and flexibility in managing the database.

Relational calculus is a non-procedural language because it focuses on specifying what data to retrieve rather than how to retrieve it. It uses mathematical predicates and quantifiers to define the desired data and leaves the actual implementation details to the database management system. This allows for a more declarative approach to querying databases, where users can express their information needs without having to worry about the specific steps to achieve them.

A foreign key is a key that establishes a relationship between two tables in a database. It is used to link a column or a set of columns in one table to the primary key of another table. This allows for the creation of relationships and ensures data integrity by enforcing referential integrity constraints. Therefore, a foreign key is the correct answer to represent the relationship between tables.

The correct answer is {t/P(t)}. This notation represents a query in the tuple relational calculus where "t" is a tuple and "P(t)" is a predicate that defines a condition on the tuple. This notation specifies that we want to retrieve all tuples "t" that satisfy the predicate "P(t)".

The count function in SQL is used to return the number of values. It counts the occurrences of a specific value or the total number of rows in a table. It does not consider the distinct values or groups, but simply counts all the values present. Therefore, the correct answer is "values".

Data independence refers to the concept that programs are not reliant on the physical or logical attributes of data. This means that the programs can operate independently of how the data is stored or organized. By separating the definition of data from the programs that use it, changes to the data structure or organization will not require modifications to the programs. Therefore, both statements 2 and 3 are correct in describing data independence.

The most commonly used operation in relational algebra for projecting a set of tuples from a relation is "Select". The Select operation allows us to retrieve specific rows or tuples from a relation based on certain conditions or criteria. It acts as a filter, selecting only the tuples that satisfy the given condition. This operation is widely used to extract the desired data from a relation and is essential for data manipulation in relational databases.

Entities can participate in a relationship in two ways: passive and active. In a passive relationship, one entity is dependent on the other entity to initiate the relationship and take action. On the other hand, in an active relationship, both entities actively participate and take action in the relationship. Therefore, the correct answer is passive and active.