Introduction to Structured Query Language (SQL)

Definition

• SQL stands for Structured Query Language.
• It is the gold standard for communicating with relational database management systems (RDBMS).

Popular SQL Databases

• Examples include:
  • MySQL
  • PostgreSQL
  • Microsoft SQL Server
  • Oracle

History

• Developed in the early 1970s.
• Initially created for IBM's System R database.
• Standardized by 1986, maintaining a popular syntax.

Relational Database Structure

Organization of Data

• Data is organized into tables (similar to Excel spreadsheets).
• Columns: Contain attributes or types of data.
• Rows: Represent individual records or data points with a unique identifier known as the primary key.

Relationships

• Establish relationships between data points using:
  • Foreign Key: The unique ID from one row stored in another table.
  • Example:
    • Teams Table: Team ID as the primary key.
    • Players Table: Team ID as the foreign key indicating which players belong to which team.
• This structure reduces duplication and redundancy in the database.

Functions of SQL

Basic Operations

• SQL is used to:
  • Read data
  • Create data
  • Update data
  • Delete data

Joining Data

• SQL can also join data based on established relationships.

SQL Syntax Overview

Components of a SQL Statement

• Statement: A piece of code that performs an action (e.g., reading, writing).
• Keywords: Special terms that manipulate the database.
  • SELECT: Used to query specific columns from a table.
  • FROM: Indicates the table to query data from.
  • WHERE: Filters results to include only records meeting certain conditions.
  • JOIN: Connects data from different tables by matching primary keys to foreign keys.

Execution

• SQL statements can be executed on various databases that support SQL.

Conclusion

• SQL provides a structured way to manage and manipulate relational data efficiently.
• Encouragement to like and subscribe for a full SQL tutorial.