What is Docker? Docker is a platform for building, running and shipping applications in a consistent manner. So, if your application works on your development machine, it can run and function the same way on other machines. With Docker, we can easily package our application with everything it needs and Read more…
The internet is made up of end-hosts, links and routers. Data is delievered hop-by-hop over each link in turn. Data is delivered in packets. A packet consistes of the data we want to be delivered, along with a header that tells the network where the packet is to be delivered, Read more…
A JOIN clause is used to combine rows from two or more tables, based on a related column between them. There are four types of join in MySQL: INNER JOIN: Returns records that have matching values in both tables LEFT JOIN: Returns all records from the left table, and the matched records Read more…
Atomicity: operations in a transaction either all succeed or all fail. Consistency: The database always transitions from one consistent state to another consistent state. The integrity of the database is not broken before the transaction starts and after the transaction ends. This means that the material written must fully comply Read more…
TRUNCATE TRUNCATE Command is a Data Definition Language operation. It is used to remove all the records from a table. It deletes all the records from an existing table but not the table itself. The structure or schema of the table is preserved. Truncate command marks the table for deallocation. This operation Read more…
dpkg is short for Debian package, a package management system developed specifically for the Debian operating system to install, update and remove software. All Linux systems derived from “Debian” use dpkg, for example “Ubuntu”. dpkg [option] <action> Options:-i: Install package-r: Remove package-P: Delete a package with its configuration file-L: Show Read more…
dpkg -l will list information about all installed packages on your system. In combination with grep, you can filter out what you want. e.g. dpkg -l | grep ftp The first column of the output is usually two letters, representing the desired state and the current state respectively. Desired state Read more…
Locate: Lookups are based on the database of the file system. The database is updated by the updatedb program. updatedb is created by the cron daemon and runs periodically. You can also generate it manually with the updatedb command. This search is a non-real-time fuzzy match. locate is faster than Read more…
Database and Table · Create Database CREATE DATABASE <database name>; CREATE DATABASE shop; · Create Table CREATE TABLE <table name> (<column name> <data type> <constrains>, <column name> <data type> <constrains>, …, <constrains of the table>,<constrains of the table>,…); CREATE TABLE product (id CHAR(4) NOT NULL, name VARCHAR(100) NOT NULL, price Read more…
A Controller servlet may perform either a forward or a redirect operation at the end of processing a request. It is important to understand the difference between these two cases, in particular with respect to browser reloads of web pages Forward A forward is performed internally by the application (servlet). Read more…