SQL

These concepts introduce more complex features and functionalities of SQL. They are essential for building more sophisticated and robust queries, managing data relationships, and optimizing query performance.

1. Subqueries and Nested Queries

   • Activities involved: Writing and using subqueries in SELECT, FROM, WHERE clauses.

   • Reason: Subqueries provide a way to perform complex queries by embedding one query within another.

   • Example Task: Write a subquery to retrieve the maximum value from a column and use it in a WHERE clause to filter results in an outer query.

2. Grouping and Aggregating Data

   • Activities involved: Using GROUP BY and HAVING clauses to group and filter aggregated data.

   • Reason: Grouping and aggregating data are necessary for summarizing data and performing aggregate calculations.

   • Example Task: Write a query that groups data by a specific column and calculates the sum for each group.

3. Indexes

   • Activities involved: Creating and using indexes to improve query performance.

   • Reason: Indexes are essential for optimizing the performance of queries on large datasets.

   • Example Task: Create an index on a table column and demonstrate its impact on query performance.

4. Views

   • Activities involved: Creating and using views to simplify complex queries.

   • Reason: Views provide a way to present data in a specific format and simplify query writing.

   • Example Task: Create a view that combines data from multiple tables and use it in a query.

5. Transactions

   • Activities involved: Using BEGIN, COMMIT, ROLLBACK to manage transactions.

   • Reason: Transactions ensure data integrity and consistency during multiple operations.

   • Example Task: Write a transaction that inserts data into two related tables and rolls back if an error occurs.