Learn database queries through 50 practical examples. Master the universal language every application uses to store and retrieve data with MySQL.
A new guide teaching SQL database management is now available.
41 pages covering queries, joins, and database design. You'll write 50 practical queries progressing from simple student lookups to sophisticated multi-table business reports.
Each query includes complete syntax, execution results, and explanations. Type every query yourself to build SQL muscle memory.
Every application stores data. Instagram saves billions of photos. Amazon tracks millions of products. Your school manages thousands of students. All this data lives in databases.
SQL is the universal language for talking to databases. Learn SQL once, use it everywhere—MySQL, PostgreSQL, Oracle, SQL Server all understand SQL with minor variations.
Backend developers write SQL connecting applications to databases. Data analysts write SQL extracting insights from data. Database administrators write SQL optimizing performance. SQL skills appear in every data-related job posting.
CBSE Class 12 students taking Computer Science (Code 083). The curriculum covers SQL extensively in Class 12.
Developers building applications requiring data storage. Anyone working with databases regardless of programming language.
Teachers needing complete query examples with solutions for classroom instruction.
Create tables defining structure with proper data types. Apply constraints preventing invalid data—primary keys ensuring uniqueness, foreign keys establishing relationships, CHECK constraints validating values.
Write SELECT queries retrieving exactly what you need. Filter using WHERE conditions. Pattern match with LIKE. Sort with ORDER BY. Calculate summaries using COUNT, SUM, AVG, MAX, MIN. Group data analyzing categories.
Join tables connecting related data. Understand INNER JOIN showing matches only versus LEFT JOIN showing all records from first table. Query across three or more tables creating comprehensive reports.
Manipulate data safely. Insert new records checking constraints. Update existing data with validation. Delete records carefully testing WHERE clauses first.
Queries 1-5: Table creation with constraints. Products validating positive prices. Employees enforcing minimum salary. Library members requiring unique contact information.
Queries 6-25: SELECT fundamentals. Books under specific prices. Authors matching patterns. Student averages by class. Top performers and low stock items. Distinct values eliminating duplicates.
Queries 26-35: Joins combining tables. Students with enrollment dates. Products with category names. Finding missing relationships—students not enrolled anywhere, products never ordered.
Queries 36-45: Data manipulation. Inserting multiple records efficiently. Updating with calculations applying discounts. Deleting with careful WHERE clauses. Copying data between tables.
Queries 46-50: Complex scenarios requiring everything learned. Students scoring above subject average using subqueries. Multi-subject failure analysis with grouping. Monthly sales reports by category joining orders, products, and dates.
SQL operations can be permanent and destructive. DELETE without WHERE removes every row. UPDATE without WHERE modifies all records. These mistakes happen in production databases causing real damage.
This guide emphasizes safety throughout. Test WHERE clauses with SELECT before DELETE. Verify UPDATE logic on small datasets first. Understand which operations are reversible (none—SQL has no undo).
Professional developers fear SQL mistakes for good reason. This guide teaches careful habits from the beginning.
No toy examples. Every query solves actual problems:
School database: Track students, courses, enrollments. Find students failing multiple subjects. Calculate class averages. Generate performance reports.
E-commerce system: Manage customers, products, orders. Find best-selling products. Calculate monthly revenue. Identify customers placing many orders.
Library management: Handle books, members, issues. Track overdue books. Find popular authors. Generate circulation reports.
These scenarios mirror real database applications you'll build professionally.
This guide teaches SQL syntax and query writing. Practice queries using:
MySQL - Free database system. Install MySQL Workbench for visual interface. Exactly what CBSE curriculum specifies.
Online SQL editors - Practice without installation. Many websites provide SQL sandboxes for testing queries.
SQLite - Lightweight database included with Python. Good for learning without server configuration.
All queries work in MySQL with minor syntax adjustments for other databases.
No programming experience required. SQL is declarative—you specify what you want, not how to get it. If you can think logically about data, you can write SQL.
The guide uses MySQL syntax following CBSE standards. Examples include table creation, sample data, and expected results.
41 pages. 779 KB. Free.
Download SQL Database Guide →
Two other Computer Science guides are available:
Python Object-Oriented Programming - Build applications that use these databases. Create classes representing database entities.
Data Structures in Python - Organize data efficiently in memory before storing persistently in databases.
Together these three cover the complete CBSE Computer Science programming curriculum for the senior-secondary level.
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Master queries, joins, and database design through 50 practical queries. Learn the universal language every application uses to store and retrieve data.
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