There are following types of keys: Primary key: The Primary key is an attribute in a table that can uniquely identify each record in a table. It is compulsory for every table. Candidate key: The Candidate key is an attribute or set of an attribute which can uniquely identify a tuple. The Primary key can be selected from these attributes. Super key: The Super key is a set of attributes which can uniquely identify a tuple. Super key is a…
ORDER BY clause helps to sort the data in either ascending order to descending order. Ascending order sort query: SELECT name,age FROM pcdsEmployee ORDER BY age ASC Descending order sort query SELECT name FROM pcdsEmployee ORDER BY age DESC The correct answer for “What is the ORDER BY clause in a database management system (DBMS)?” would be: “The ORDER BY clause is used in SQL (Structured Query Language) to sort the result set of a query in ascending or descending…
Redundancy control Restriction for unauthorized access Provides multiple user interfaces Provides backup and recovery Enforces integrity constraints Ensure data consistency Easy accessibility Easy data extraction and data processing due to the use of queries The advantages of a Database Management System (DBMS) include: Data Centralization: DBMS allows for centralized control and management of data, ensuring data consistency and integrity across the organization. Data Sharing: Multiple users and applications can access the same data simultaneously, promoting data sharing and collaboration. Data…
The DML Compiler translates DML statements in a query language that the query evaluation engine can understand. DML Compiler is required because the DML is the family of syntax element which is very similar to the other programming language which requires compilation. So, it is essential to compile the code in the language which query evaluation engine can understand and then work on those queries with proper output.
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 as extension or database state or snapshot. It is time dependent. Intension: Intension is also known as Data Schema and defined as the description of the database, which is specified during database…
DBMS Interview Questions – Set 11 DBMS Interview Questions – Set 10 DBMS Interview Questions – Set 09 DBMS Interview Questions – Set 08 DBMS Interview Questions – Set 07 DBMS Interview Questions – Set 06 DBMS Interview Questions – Set 05 DBMS Interview Questions – Set 04 DBMS Interview Questions – Set 03 DBMS Interview Questions – Set 02 DBMS Interview Questions – Set 01
INNER JOIN Inner join shows matches only when they exist in both tables. Example in the below SQL there are two tables Customers and Orders and the inner join in made on Customers.Customerid and Orders.Customerid. So this SQL will only give you result with customers who have orders. If the customer does not have order it will not display that record. SELECT Customers.*, Orders.* FROM Customers INNER JOIN Orders ON Customers.CustomerID =Orders.CustomerID LEFT OUTER JOIN Left join will display all…
The Checkpoint is a type of mechanism where all the previous logs are removed from the system and permanently stored in the storage disk. There are two ways which can help the DBMS in recovering and maintaining the ACID properties, and they are- maintaining the log of each transaction and maintaining shadow pages. So, when it comes to log based recovery system, checkpoints come into existence. Checkpoints are those points to which the database engine can recover after a crash…
Relational Algebra is a Procedural Query Language which contains a set of operations that take one or two relations as input and produce a new relationship. Relational algebra is the basic set of operations for the relational model. The decisive point of relational algebra is that it is similar to the algebra which operates on the number. There are few fundamental operations of relational algebra: select project set difference union rename,etc.
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 better transaction processing performance. It is a prototype which is formed to show that it is possible to build a Relational System that can be used in a real-life environment to solve real-life problems. Following are…