Database Fundamentals IV

What is the primary purpose of fields (or columns) in a Database Management System (DBMS)

• They speed up the performance of the database queries.

• the dictate user permissions in the database

• They define the relationship between different tables

• They represent specific categories of a data table.

Answer explanation

Fields (or columns) in a DBMS represent specific categories or attributes of data within a table. Each field contains data for a specific characteristic, like a 'name' field in a 'users' table. While permissions can be set at various levels within a database, fields or columns don't directly dictate user permissions. Their primary role is related to data organization within a table. While organizing data into appropriate fields or columns can help with making data retrieval more efficient, their main purpose isn't to improve database query performance. Enhancing query speed directly is usually done through other means, like indexing or query optimization. Relationships between tables are typically defined using keys (like primary keys and foreign keys) and constraints, not directly by fields or columns.

Which of the following BEST describes semi-structured data?

• Unstructured data includes clear relationships and hierarchy among data elements

• semi-structured data has organized elements but doesn't strictly adhere to a tabular format

• stuctured data is always in a tabular format

• semi-stuctured data is always in a non- tabular format

Answer explanation

Semi-structured data is a mix of raw data and structured data. It possesses some organizational properties that make it easier to process but doesn't strictly adhere to a rigid tabular format like structured data. While semi-structured data often doesn't adhere to a strict tabular format, it isn't always in a non-tabular format. Structured data is organized and can easily be processed and analyzed. While semi-structured data has some structure, it doesn't always fall into a tabular format. Unstructured data lacks a defined structure, unlike semi-structured data that has some organizational elements that define relationships among data entities.

Sarah, a software engineer, is working on a project that involves managing and querying data stored as complex and nested objects. Her team lead suggested using a document database. What makes a document database a suitable choice for handling this type of data?

• Document database can't handle complex, nested data.

• Document database store data as flexible documents , often in format Like JSON

• Document database require a predefined schema

• Document database organize data in a rigid tabular structure.

Answer explanation

Document databases store data as flexible, self-describing documents, typically but not exclusively in formats like JSON. This allows them to represent complex and hierarchical data efficiently within a single document. One of the key features of document databases is their schema-less nature. They do not require a predefined schema and offer flexibility to store data. Document databases are actually designed to handle complex and nested data quite well. Their nature allows them to easily store and manage data as documents (which can contain nested data), typically in formats like JSON. Document databases do not require a fixed, rigid tabular structure like a relational database does. They are flexible and can manage data in formats like JSON, which supports nested objects.

When populating a database, what does import/input refer to?

• adding data records to the database manually or by importing from another source.

• queying data from the database

• Transferring the database to another server.

• deleting data from the database

Answer explanation

Import/input refers to the process of populating the database with data records. This can be done manually, often through a form, or by importing data from another source such as a file or another database. While data can be transferred between servers, import/input specifically refers to the process of adding data to the database. Import/input refers to adding data to the database, not removing it. Querying refers to extracting specific information from the database, not adding data to it.

When working with databases, which definition BEST describes a table?

• A system to ensure the security of the database

• the software used to manage the database.

• The rows that that the actual data values

• The structure consisting of rows and columns that hold data

Answer explanation

In a relational database, a table is a structure that consists of rows and columns. Each row represents a unique record, and each column represents a specific field or attribute of the data. While rows are indeed a part of a table, they represent individual records or entries, not the table itself. The software used to manage the database is known as a database management system (DBMS), not a table. While security is an important aspect of databases, it is not what the term 'table' refers to. A table is a structure to hold data.

In which of the following scenarios would a database manager need to use the ALTER command?

• When they need to retrieve specific data from a table

• when they need to delete a record from a table

• When there's a requirement to add a new column to an existing table

• When they want to create a new table in the database.

Answer explanation

The ALTER command is used to add, delete/drop or modify columns in an existing table. The DELETE command, not the ALTER command, is used to remove records from a table. The SELECT statement, not the ALTER command, is used to retrieve data from a database. The CREATE command, not the ALTER command, is used to create a new table in the database

What is a primary key in a database?

• A key used to sort data

• A key that connects multiple databases

• A key that uniquely identifies each record

• A key use to secure the database.

Answer explanation

Explanation

A primary key is a specific type of field or column in a database table that uniquely identifies each record in that table. The primary key must contain unique values, and it cannot contain NULL values. Its purpose is to ensure data integrity and facilitate efficient data retrieval. While primary keys can help in organizing data, their main purpose is to uniquely identify each record in a database table, not sorting data. While keys can establish relationships between tables, a primary key's primary role is to uniquely identify records within a single database table, not to link multiple databases. While data security is crucial, a primary key's main role is to uniquely identify records in a database, not to provide security.

Alejandro is a database administrator for an e-commerce company. A customer has just requested that their account and all related personal data be permanently deleted from the company's database. Which SQL command should Alejandro use to remove this customer's information from the company's database?

• Insert

• Select

• Delete

• Update

Answer explanation

Alejandro should use the DELETE command. This command is used to remove existing records from a database. With the DELETE command, he can remove the specific customer's information from the company's database. The INSERT command is used to add new records into a database, not for deleting records. The UPDATE command is used for modifying existing records in a database, not for deleting records. The SELECT command is used to retrieve data from a database, not for deleting records.