Introduction to Databases and SQL

Overview of Databases

• Purpose: Used for creating and managing the repository for storing and retrieving data.
• Database Management System (DBMS): Serves as an interface between the end user and the dbms software.
• Example: Train ticket booking system, where data is fetched from a backend database displayed on a front-end interface.

Importance of DBMS

• Allows data to be stored and effectively retrieved.
• Requires Structured Query Language (SQL) for operations.

SQL (Structured Query Language)

• Definition: A language for managing and retrieving data effectively within a Relational Database Management System (RDBMS).
• Need: Necessary to avoid complex handling of file systems, which are tedious for structured data.
• Data Structure: Utilizes table data structures with rows and columns.

SQL Fundamentals

• Based On: Relational algebra and relational calculus.
• ANSI Standard: SQL is built upon this standard.
• Supported Software: Microsoft SQL Server, Informix, Oracle, MySQL, Sybase.

Features of SQL

• Query Statements: English-like syntax for easy understanding.
  • Example: DELETE TABLE employee removes the table named "employee".
• Case Sensitivity: SQL queries are not case-sensitive.
• Multiple Solutions: Different ways to execute a query.

Execution of SQL Queries

• Components Involved:
  • SQL engine, optimization engine, query engine, query dispatchers.
• Process: DBMS accepts the query, chooses the best execution plan, and provides results to the user, usually in table format.

Types of SQL Sub-languages

1. DDL (Data Definition Language)
2. DML (Data Manipulation Language)
3. DCL (Data Control Language)
4. TCL (Transaction Control Language)

Schema and Table Structure

• Schema: Represents the structure of a table, including columns and data types.
• Example Table:
  • Columns: ID number, Name, Department Name, Salary
  • Types: Numeric and Character data types.
• Data Example:
  • John Abraham, ID1, working in Quality Assurance Department with a specified salary, stored in interconnected rows and columns.

Conclusion

• Topics Covered: Basics of SQL, types of SQL sub-languages, and table schema structure.
• Future presentations will cover DDL, DML, DCL, TCL in detail.

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