Core Concepts

Understanding the fundamental concepts of relational databases is key to effectively utilizing SQL Server. This section covers essential topics such as tables, rows, columns, primary keys, foreign keys, and the relational model itself.

Tables and Schemas

Data in SQL Server is organized into tables. A table is a data structure that organizes data into rows and columns. Schemas provide a way to group database objects such as tables, views, and stored procedures.

Keys and Relationships

Primary keys uniquely identify each record (row) in a table. Foreign keys establish relationships between tables by referencing the primary key of another table, ensuring data integrity through referential constraints.

Transact-SQL (T-SQL)

Transact-SQL (T-SQL) is Microsoft's proprietary extension to SQL, the standard language for managing and manipulating databases. T-SQL adds procedural programming, local variables, string and date processing functions, and other extensions.

Data Manipulation Language (DML)

DML statements are used to retrieve, insert, update, and delete data in database tables. Key DML commands include SELECT, INSERT, UPDATE, and DELETE.

-- Example: Inserting a new record
INSERT INTO Customers (CustomerID, CompanyName, ContactName)
VALUES (10, 'Example Corp', 'John Doe');

Data Definition Language (DDL)

DDL statements are used to define, modify, and delete database objects. Key DDL commands include CREATE TABLE, ALTER TABLE, and DROP TABLE.

-- Example: Creating a new table
CREATE TABLE Products (
    ProductID INT PRIMARY KEY,
    ProductName VARCHAR(255),
    Price DECIMAL(10, 2)
);

Database Design and Normalization

Effective database design is crucial for performance, maintainability, and data integrity. Normalization is a process used to organize data in a database, which includes creating tables and establishing relationships between them according to rules designed to protect data by dividing larger tables into smaller tables and linking them by relationships.