SQL Introduction

SQL, or Structured Query Language, is a programming language designed for managing and manipulating relational databases.

It is used to communicate with and manage databases by performing various operations such as querying data, updating data, inserting data, and deleting data.

Here are some key concepts and components of SQL.

Database: A database is a structured collection of data stored in a computer, organized in a way that allows for efficient retrieval and management. SQL is commonly used to interact with relational databases, which organize data into tables with rows and columns.
Table: In a relational database, data is stored in tables. A table is a collection of rows and columns, where each row represents a record, and each column represents a field or attribute of that record.
Schema: A schema is a collection of database objects, including tables, views, indexes, and procedures. It defines the structure and organization of the database.
Query: SQL allows users to write queries to retrieve data from a database. The most common query is the SELECT statement, which is used to fetch data from one or more tables based on specified conditions.
```
SELECT column1, column2 FROM table_name WHERE condition;
```
Insert: The INSERT statement is used to add new records (rows) to a table.
```
INSERT INTO table_name (column1, column2) VALUES (value1, value2);
```
Update: The UPDATE statement is used to modify existing records in a table.
```
UPDATE table_name SET column1 = value1 WHERE condition;
```
Delete: The DELETE statement is used to remove records from a table.
```
DELETE FROM table_name WHERE condition;
```
Primary Key: A primary key is a unique identifier for a record in a table. It ensures that each record can be uniquely identified, and it cannot have a NULL value.
Foreign Key: A foreign key is a column or a set of columns in a table that refers to the primary key of another table. It establishes a link between the two tables.
Normalization: Normalization is the process of organizing the data in a database to eliminate redundancy and dependency. It involves dividing large tables into smaller, more manageable tables and defining relationships between them.

SQL is widely used in various applications and plays a crucial role in data management and retrieval in modern information systems.

There are different flavors of SQL, such as MySQL, PostgreSQL, Microsoft SQL Server, and Oracle SQL, but they all share the same fundamental principles and syntax for querying and manipulating databases.

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