What are the three levels of data abstraction? Following are three levels of data abstraction: Physical level: It is the lowest level of abstraction. It describes how data are stored. Logical level: It is the next higher level of abstraction. It describes what data are stored in the database and what the relationship among those data is. View level: It is the highest level of data abstraction. It describes only part of the entire database. For example– User interacts with the system using…

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What is data abstraction in DBMS? Data abstraction in DBMS is a process of hiding irrelevant details from users. Because database systems are made of complex data structures so, it makes accessible the user interaction with the database. For example: We know that most of the users prefer those systems which have a simple GUI that means no complex processing. So, to keep the user tuned and for making the access to the data easy, it is necessary to do data…

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What is functional Dependency? Functional Dependency is the starting point of normalization. It exists when a relation between two attributes allow you to determine the corresponding attribute’s value uniquely. The functional dependency is also known as database dependency and defines as the relationship which occurs when one attribute in a relation uniquely determines another attribute. It is written as A->B which means B is functionally dependent on A. Explain ACID properties ACID properties are some basic rules, which has to…

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What is a database system? The collection of database and DBMS software together is known as a database system. Through the database system, we can perform many activities such as- The data can be stored in the database with ease, and there are no issues of data redundancy and data inconsistency. The data will be extracted from the database using DBMS software whenever required. So, the combination of database and DBMS software enables one to store, retrieve and access data…

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What are indexes? What are B-Trees Index makes your search faster. So defining indexes to your database will make your search faster.Most of the indexing fundamentals use “B-Tree” or “Balanced-Tree” principle. It’s not a principle that is something is created by SQL Server or ORACLE but is a mathematical derived fundamental.In order that “B-tree” fundamental work properly both of the sides should be balanced. What is a Sub-Query A query nested inside a SELECT statement is known as a subquery…

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What is Data Warehousing Data Warehousing is a process in which the data is stored and accessed from central location and is meant to support some strategic decisions. Data Warehousing is not a requirement for Data mining. But just makes your Data mining process more efficient. Data warehouse is a collection of integrated, subject-oriented databases designed to support the decision-support functions (DSF), where each unit of data is relevant to some moment in time. What is the default “-SORT” order…

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Can you explain Fourth Normal Form and Fifth Normal Form In fourth normal form it should not contain two or more independent multi-v about an entity and it should satisfy “Third Normal form”. Fifth normal form deals with reconstructing information from smaller pieces of information. These smaller pieces of information can be maintained with less redundancy. What is order by clause ORDER BY clause helps to sort the data in either ascending order to descending order. Ascending order sort query:…

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Can you explain the SELECT INTO Statement SELECT INTO statement is used mostly to create backups. The below SQL backsup the Employee table in to the EmployeeBackUp table. One point to be noted is that the structure of pcdsEmployeeBackup and pcdsEmployee table should be same. SELECT * INTO pcdsEmployeeBackup FROM pcdsEmployee What is SQL SQL stands for Structured Query Language.SQL is an ANSI (American National Standards Institute) standard computer language for accessing and manipulating database systems. SQL statements are used…

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Introduction to RDBMS Introduction Data is meaningful information. Database is a collection of relevant data. DBMS means database management system. DBMS provides the software to manage the database. Following are the operations to be performed on database: insertion, deletion, updation, sorting, searching, traversing, etc. Following are the different types of DBMS: FMS, Hierarchical, DBMS FMS (File Management System) It is simple to create but difficult to manage. No relations are there (like 1-to-1, 1-to-many) Hierarchical System Here data is stored…

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