Relational Algebra

Relational algebra, first described by E.F. Codd while at IBM, is a family of algebra with a well-founded semantics used for modelling the data stored in relational databases, and defining queries on it. To organize the data, first the redundant data and repeating groups of data are removed, which we call normalized. By doing this

Installing and configuring tomcat on Centos 7

wget http://www.us.apache.org/dist/tomcat/tomcat-7/v7.0.57/bin/apache-tomcat-7.0.57.tar.gz tar -xvvf apache-tomcat-7.0.57.tar.gz mv apache-tomcat-7.0.57 /opt/tomcat nano /opt/tomcat/conf/tomcat-users.xml find the <tomcat-users> </tomcat-users> lines and in between add the below entry <role rolename="manager-gui"/> <role rolename="manager-script"/> <role rolename="manager-jmx"/> <role rolename="manager-status"/> <role rolename="admin-gui"/> <role rolename="admin-script"/> <user username="admin" password="admin" roles="manager-gui,manager-script,manager-jmx,manager-status,admin-gui,admin-script"/> and save the file and then issue command chmod 755 /opt/tomcat sh /opt/tomcat/bin/startup.sh  

Installing and configuring Mysql server on Freebsd

Go to the /usr folder cd /usr and then extract updates portsnap fetch extract then go to mysql client folder in ports(the version may change on your ports version and updates) /usr/ports/databases/mysql56-client then issue the command to install client make install clean and then navigate to the server folder cd /usr/ports/databases/mysql56-server then install it make

Jdk installation javaws error javaws: error while loading shared libraries: libX11.so.6: cannot open shared object file: No such file or directory

javaws -version [root@centos ~]# javaws: error while loading shared libraries: libX11.so.6: cannot open shared object file: No such file or directory -bash: javaws:: command not found install this package yum -y install libX11-devel.x86_64 and then magic happens [root@centos ~]# javaws -version Java(TM) Web Start 10.71.2.14-fcs Usage: javaws [run-options] <jnlp-file> javaws [control-options]