Its a visual editor by default installed in every linux system. The next version of vi is vim. The vi editor tool is an interactive...

1. yum install postgresql-server postgresql-contrib 2. su postgresql 3. postgresql-setup initdb 4. vi /var/lib/pgsql/data/pg_hba.conf 5. Find the lines that look like this near the end...

In normal PostgreSQL operation, tuples that are deleted or obsoleted by an update are not physically removed from their table. They remain present until a VACUUM is done. Therefore...

To restore a database from the default directory /backup/rman use the cmd cmd: RESTORE DATABASE; Restore Specific Tablespace: Instead of restoring the full database, you can...

1. View Current RMAN Configuration Before we take the backup, we have to configure certain RMAN parameters. For example, how long you want to reatain...

A database administrator’s responsibilities can include the following tasks: Installing and upgrading the Oracle Database server and application tools Allocating system storage and planning future...

Go to orcale.com Go to downloads as shown in the image and select the compataible version of the system by accepting the license and click...

Features: ->MongoDB is a No SQL database. It is an open-source, cross-platform, document-oriented database written in C++.C-> It stores data as documents, so it is known...

-> SQLite is an open source, zero-configuration, self-contained, stand alone, transaction relational database engine designed to be embedded into an application. -> SQLite does not have...

-> This is the world’s second most popular and widely used open source database. -> All the database names, table names and table fields name are...

-> Its relational database management system used in enterprise applications. -> Its biggest competitor is Microsoft SQL Server. -> Runs on Windows,Unix,Linux and Mac Operating...

1. To Find the nth highest salary Eg: General query for all Database SELECT DISTINCT salary FROM emp X WHERE n = ( SELECT COUNT(DISTINCT...

High availability: Database servers can work together to allow a second server to take over quickly if the primary server fails. Load balancing: To allow...

Create Database: -> A database is a named collection of SQL objects (“database objects”). Generally, every database object (tables, functions, etc.) belongs to one and...

-> A role can be thought of as either a database user, or a group of database users, depending on how the role is set...

To list all the users: cmd:cat /etc/passwd To delete the user in linux: -> we can able to delete the users from ther root user...

listen_addresses (string) -> Specifies the TCP/IP address(es) on which the server is to listen for connections from client applications. -> The special entry ‘*’ corresponds...

-> To rename already existing table Syntax: ALTER TABLE table_name RENAME to new_table_name; Eg: Alter table attribute rename to attribute1; -> To rename a column...

-> If we want to retrun boolean value from the query or more than one result based on the condition then we can use case...

-> To truncate the instance table locks i.e. when one user locked the object and the user wants to lock the same object then dead...