Data manipulation is the handling of data in a database server. The data is handled and manipulated by using different types of commands which are present in a query. It helps us perform different types of operations on databases. There are four data manipulation commands. Insert It is used to insert data into the table. It can be used for adding more data to a pre−existing table. The motive is to insert the data into the table by using an INSERT statement. Syntax INSERT INTO table_name(parameters) VALUES (values_for_parameter); Here, table_name is the name of the ... Read More

Data management that allows to access data from devices is the main problem. The mobile database allows applications to access data from devices even when on the move. It is a database that connects devices over a wireless network. Here, the client and server have a wireless connection. The wired connections have the entire database distributed with full or partial replication. Fixed hosts are there to perform data management with the help of database servers. Base stations are present at fixed locations to pass communication with the mobile units to and from the fixed hosts. Issues that arise in ... Read More

Data distribution is done through consistent hashing to make the data evenly distributed across the nodes in a cluster. Instead of getting rows of table on a single node, rows gets distributed across the clusters which make the load of table data get evenly divided. The partition key is used to distribute data among nodes and determine data locality. In Cassandra, data distribution and replication work together. Mainly depends on three things i. e. partition key, key value, and token range. Cassandra Table This table consists of two rows in which one row has four columns followed by ... Read More

A temporary work area known as a cursor is established in the system memory whenever DML statements are performed. Although a cursor may contain many rows, processing−wise, only one row is taken into consideration. Cursors are very helpful to the kind of DBMSs like Oracle, Mysql, SQL servers, etc. A cursor is a control structure to go through database records and is used in databases. Cursors are of two types Implicit Cursors Explicit Cursors Implicit Cursors If you don't use an explicit cursor for the statement, Oracle will create implicit cursors while the SQL statement is performed. Some ... Read More

Catalogs are referred to as database systems that contain information about objects present in the database itself or the database itself that contains metadata of a distributed database. Catalog management is to be handled effectively as it will affect the performance of site autonomy, view management, and data distribution and replication. Distributed catalog management knows the data distribution across the sites. If any fragmentation and replication of relation occur, then with the help of a distributed catalog, we can uniquely find the replica of each fragment. Global relation name is shown as , and Global replica name is ... Read More

Distributed Consensus Distributed consensus plays a vital role in decentralized systems, ensuring reliability, fault tolerance, and agreement among multiple parties. Distributed consensus occurs when multiple parties try to accept some values, which is difficult as agreeing is not easy. The complexity to achieve consensus increases as an increase in the number of parties agree on an agreement. Various sites are working together to do a common task by communicating with each other via a network and agreeing to some values which come under distributed consensus. Importance of Distributed Consensus in Distributed Systems In a distributed or decentralized multi−agent platform, ... Read More

The transfer of data for storage at various computers or locations connected over a network is known as a distributed database. It may alternatively be described as a database that gathers information from several databases using independent computers linked by data communication connections. Compared to centralized database systems, distributed databases can offer higher availability and dependability. This is so that the system can continue to function even if one or more sites go down. A distributed database system can perform more effectively by distributing the burden and using the information across several sites. Design Considerations ... Read More

A document is a record in a document−based database that contains data on an item and any associated metadata. Field−value pairs form documents that can include a variety of data types like characters, integers, dates, arrays, and objects. They are commonly saved in XML, JSON, or BSON formats. Data retrieval and processing are made simple by the unique identifiers assigned to each document in the database. Documents do not have a set schema, therefore they do not all need to contain the same fields in a collection. This adaptability makes it possible to store several data structures in ... Read More

Database management systems (DBMS) employ the non−procedural query language known as Domain Relational Calculus (DRC). DRC focuses simply on what data to collect without outlining the techniques for retrieval, as opposed to Relational Algebra, which provides methods and procedures for fetching data. It offers a declarative method of database querying. Syntax { | P(x1, x2, ..., xn) } Here, refers to the resulting domain variable P(x1, x2, ..., xn) refers to the condition equivalent to the predicate calculus. Example 1 This example shows us to solve the query which is how to find the names ... Read More

Double buffering is essential for improving user experience and performance. This method is extensively used to reduce delays, increase performance, and enable smooth multitasking in database management systems, streaming media applications, and graphics rendering. In order to optimise data transit and processing, double buffering is used which is a programming approach that uses two buffers or temporary storage spaces. It enables the execution of input and output processes simultaneously, thereby minimising delays and enhancing system performance as a whole. Double buffering allows for efficient multitasking and effective resource management by using one buffer for data storage while the other ... Read More