Found 1719 Articles for Big Data Analytics

Transaction Control language is a language that manages transactions within the database.It is used to execute the changes made by the DML statements.TCL CommandsTransaction Control Language (TCL) Commands are:Commit − It is used to save the transactions in the database.Rollback − It is used to restore the database to that state which was last committed.Begin − It is used at the beginning of a transaction.Savepoint − The changes done till savpoint will be unchanged and all the transactions after savepoint will be rolled back.ExampleGiven below is an example of the usage of the TCL commands in the database management system ... Read More

Data control language (DCL) is used to access the stored data. It is mainly used for revoke and to grant the user the required access to a database. In the database, this language does not have the feature of rollback.It is a part of the structured query language (SQL).It helps in controlling access to information stored in a database. It complements the data manipulation language (DML) and the data definition language (DDL).It is the simplest among three commands.It provides the administrators, to remove and set database permissions to desired users as needed.These commands are employed to grant, remove and deny ... Read More

The structured query language (SQL) commands deal with the manipulation of data present in the database that belongs to the DML or Data Manipulation Language. This includes most of the SQL statements.Examples of DMLThe examples of DML in the Database Management System (DBMS) are as follows −SELECT − Retrieve data from the database.INSERT − Insert data into a table.UPDATE − Update existing data within a table.DELETE − Delete records from a database table.Syntax for DML CommandsThe syntax for the DML commands are as follows −INSERTInsert command is used to insert data into a table.The syntax for INSERT command is as ... Read More

Data definition language (DDL) is a language that allows the user to define the data and their relationship to other types of data.Data Definition language statements work with the structure of the database table.Various data types used in defining columns in a database tableIntegrity and value constraintsViewing, modifying and removing a table structureDDL CommandsThe Data Definition Languages (DDL) Commands are as follows −Create − It is used to create a new table or a new database.Alter − It is used to alter or change the structure of the database table.Drop − It is used to delete a table, index, or ... Read More

Once data is stored or filled it requires manipulation like insertion, deletion, updating, and modification of data. For these operations a set of languages are provided by the database management system (DBMS). So, the database languages are used to read, update and store data in the database.The different types of DBMS languages are as follows −Data Definition Language (DDL) − Create, Drop, Truncate, Rename.Data Manipulation language (DML) − Select, Insert, Delete, Update.Data Control Language (DCL) − Revoke, Grant.Transaction Control Language (TCL) − Rollback, Commit.The DBMS languages are pictorially represented as follows −Data Definition Language (DDL)It is a language that allows ... Read More

A Data Dictionary is an integral part of a database. It holds the information about the database and the data that it stores called as metadata.A meta data is the data about the data.It is the self-describing nature of databases.It holds the information about each data element in the database.Such as names, types, range of values, access authorization, indicate which application program uses the data.Meta data is used by the developers to develop the program, queries to manage and manipulate the data.Types of dictionariesIn general, DBMS data dictionaries are of two types. These dictionaries are as follows −Active data dictionaryIt ... Read More

A database administrator (DBA) is a person or group in charge of implementing DBMS in an organization. The DBA job requires a high degree of technical expertise. DBA consists of a team of people rather than just one person.The primary role of Database administrator is as follows −Database designPerformance issuesDatabase accessibilityCapacity issuesData replicationTable MaintenanceResponsibilities of DBAThe responsibilities of DBA are as follows −Makes the decision concerning the content of the database.Plans the storage structure and access strategy.Provides the support to the users.Defines the security and integrity checks.Interpreter backup and recovery strategies.Monitoring the performance and responding to the changes in the ... Read More

Normalization is the process of organizing the data in a database. It helps in removing the duplicate values in the database. Normalization divides the large table into smaller tables and links them using relationships.The normal form is used to reduce redundancy from the database table. Normalization is the name given to the process of simplifying the relationship among data elements in a record.In simple words we can say, Normalization is the process of organizing data to minimize.Redundancy/duplication/repetition.Insertion, deletion, updating anomalies.Normal formsThere are six Normal forms which are as follows −First Normal Form (1NF)Second Normal Form (2NF)Third Normal Form (3NF)Boyce-Codd Normal ... Read More

A trigger is a procedure which is automatically invoked by the DBMS in response to changes to the database, and is specified by the database administrator (DBA). A database with a set of associated triggers is generally called an active database.Parts of triggerA triggers description contains three parts, which are as follows −Event − An event is a change to the database which activates the trigger.Condition − A query that is run when the trigger is activated is called as a condition.Action −A procedure which is executed when the trigger is activated and its condition is true.Use of triggerTriggers may ... Read More

Let’s see the procedure to access database users in DBMS step by step.Step 1 − The request from the user is passed to the DBMS user interface, where oracle engine locates the files for the given relation.The relation is nothing but − table schemaLinking between the recordsStep 2 − The file manager will generate the particular file for the given table and process this request to the disk manager.Step 3 − The disk manager will give the offset address for the given table where the records are stored.Step 4 − The displacement of a particular block is done from hard ... Read More