Working in Agile mode became a golden standard throughout the past few decades for many leading companies in several different sectors of the market. In fact, several branches and methodologies of Agile exist for every working environment. In this article you will learn the basic concepts of Agile in Software…
In this article you will learn about some most important concepts of the Object Oriented Design. Moreover, you will be introduced to UML diagrams and to some common application design principles. Object Oriented Programming The OOP consists of: Objects Classes Abstraction Polymorphism Inheritance Encapsulation Abstract classes Serve to represent an…
The existence of each company is justified by a goal to be achieved, a mission to accomplish. But no business can operate without human resources. The human resources department is at the same level of importance within a company as other services essential to its proper functioning and the achievement…
The purpose of this article is to teach the concepts of the Object Oriented Programming (OOP) to a novice programmer as quickly and easily as possible. Additionally, this information will help you to refresh your knowledge and possibly to prepare you for a job interview. Note: The examples of code…
The Data Definition Language is the part of the SQL language that allows you to perform operations on the objects that make up the structure of a database (i.e. the container). These objects are TABLES, VIEWS or INDEX. (The present section focuses on the manipulation of tables and indexes, the…
The UNION clause makes it possible to add the result of two or more queries. Exactly as if we were doing only one query from several separate queries. select statement 1 UNION select statement 2 UNION select statement 3 … In addition, the UNION clause naturally eliminates the resulting duplicates.…
A subquery is a SELECT statement that can be used against an unknown value (which is then known when the subquery is performed). In fact, subqueries are an indirect way to relate multiple tables, since the subquery can be built on a table other than the main query. A subquery…
1.1 Statistical functions The statistical functions are standard to SQL and allow the calculation of statistical results on the rows of a table. AVG (column) Average values SUM (column) Sum of values MIN (column) Minimum value MAX (column) Maximum value COUNT (column) Number of values in the column COUNT (DISTINCT…
When two tables are matched in a query, a join is made. The goal is to relate the data of one table with the data of another table. The result is to have the rows of two tables side by side. For this to be feasible and for the relationship…
1.1 The conditional expression SQL determines on which lines will be performed an operation by means of a conditional expression in the WHERE clause. At each line of the table, the expression conditional is re-evaluated based on line-specific values. If the expression evaluates to TRUE, then the requested operation (SELECT,…