Gateway for Preparing Interviews
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. … Read more
What is System R? How many of its two major subsystems? System R was designed and developed from 1974 to 1979 at IBM San Jose Research Centre. System R is the first implementation of SQL, which is the standard relational data query language, and it was also the first to demonstrate that RDBMS could provide … Read more
What do you mean by extension and intension? Extension: The Extension is the number of tuples present in a table at any instance. It changes as the tuples are created, updated and destroyed. The actual data in the database change quite frequently. So, the data in the database at a particular moment in time is known … Read more
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 … Read more
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. … Read more
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 … Read more
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 … Read more
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 … Read more
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 … Read more
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 … Read more