OOP and SQL Concepts

**OOP** **C\#** It is an object-oriented programming language created by Microsoft that runs on the.NET Framework. C\# has roots from the C family, and the language is close to other popular languages like C++ and Java. The first version was released **in 2002**. The **.NET framework** helps you...

**OOP** **C\#** It is an object-oriented programming language created by Microsoft that runs on the.NET Framework. C\# has roots from the C family, and the language is close to other popular languages like C++ and Java. The first version was released **in 2002**. The **.NET framework** helps you build web apps, desktop apps, and web services. **.NET** core is for creating cross-platform cloud apps that run on Windows, Mac, and Linux. The **MAIN METHOD** is the entry point of a C\# application. **Namespaces** are used in C\# to organize and provide a level of separation of codes. **Console.WriteLine**(\"Creating my namespace\"); **Constants** are immutable values which are known at compile time and do not change for the life of the program. Use **PascalCase** for class names and method names. Use **camelCase** for method parameters and local variables. Use **PascalCase** for constant names, both fields and local constants. **Coding Principles** - - - - - **Console.ReadLine()**; USE TO READ USER OUTPUT **object-oriented programming** is about creating objects that contain both data and methods. A **class** is a template for objects, and an object is an instance of a class. Fields and methods inside classes are often referred to as \"**Class Members**\": When the individual objects are created, they inherit all the variables and methods from the class. Variables inside a class are called **FIELDS** **Access Modifiers** are keywords that define the accessibility of a member, class or datatype in a program. **Public** The code is accessible for all classes **Private** The code is only accessible within the same class **Protected** The code is accessible within the same class, or in a class that is inherited from that class. **Internal** The code is only accessible within its own assembly, but not from another assembly. A **Method** is a function inside our Class that contains a series of statements. A **Property** in C\# is a member of a class that is used to set and get the data from a data field (i.e. variable) of a class. The **Accessors** are nothing but special methods which are used to set and get the values from the underlying data member (i.e. variable) of a class. This **set** accessor contains a fixed variable named value. A **constructor** is a special method that is used to initialize objects. **Encapsulation** is defined as the wrapping up of data and information under a single unit. **Advantages of Encapsulation** - - - - **PUBLIC** keyword It is called an access modifier, which specifies that the color variable/field of Car is accessible for other classes as well, such as Program. **DBMS** **Advantages of Using DBMS** - - - - **MS SQL Server** is a relational database management system (RDBMS) developed by Microsoft. **Relationships** in SQL tables define how tables are connected to one another. **Structured Query Language** is a standardized programming language used to manage and manipulate relational databases. The **WHERE** clause in SQL is used to filter records and specify the conditions that must be met for a query The **ORDER BY** clause in SQL is used to sort the result set of a query by one or more columns The **DISTINCT** keyword in SQL is used to remove duplicate values from the result set Returns the number of rows that match a specified condition The **SUM** calculates the total sum of a numeric column. **MAX**: Returns the maximum value from a numeric column. **MIN**: Returns the minimum value from a numeric column. The **GROUP BY** clause in SQL is used to group rows that have the same values in specified columns into summary rows The **HAVING** clause in SQL is used to filter the results after GROUP BY has been applied, similar to how the WHERE clause A **correlated subquery** is a subquery in SQL that refers to values from the outer query. **Full-Text Search** is a database technique which will retrieve records A **JOIN** is used in SQL to combine rows from two or more tables based on a related column. **Right Joints** select all the columns in the Right table and only the matching records from the left table The **UNION** operation combines the results of two queries and removes duplicate rows from the final output. The **INTERSECT** operation returns only the rows that are present in both queries (common values). The **EXCEPT** operation returns rows from the first query that are NOT in the second query. **core principles** 1\. Data Integrity 2\. Avoiding Redundancy 3\. Normalization 4\. Entity Relationships 5\. Use of Constraints 6\. Scalability and Performance **Entity relationship (ER) Modeling** A visual approach of representing the structure of a database by identifying and defining the different entities (objects or concepts) within the data and how they are related to each other through relationships. **Entity Relationship Cardinality (ERD)** This defines the number of instances of one entity that can be linked to the number of instances of another entity. A **FOREIGN KEY** (FK) is a column or combination of columns that is used to establish and enforce a link between the data in two tables **Constraints** are used to limit the type of data that can go into a table. **Normalization** - is the process of organizing data within tables in a specific manner to organize data efficiently. **Denormalization** - is also the method which is used in a database. It is a technique in which data are combined to execute the query quickly. **Main goal of normalization is**: - - - **Relational database design principles** are guidelines for organizing data in tables to ensure data integrity and efficiency. **Relational Database Design Principles** - Ensure accuracy and consistency (e.g., primary key uniqueness). - Store data once and reference it. - Optimize for efficient queries and updates. - Use ER diagrams to represent relationships clearly. - Apply rules to structure data to reduce redundancy.