Warm-Up For SQL: Basic Concepts

• What is the difference between a SELECT statement and a CREATE TABLE statement? A SELECT statement retrieves data from existing tables. A CREATE TABLE statement defines a new table structure with columns and data types.
• Explain the concept of primary keys and foreign keys.A primary key uniquely identifies each row in a table. A foreign key references a primary key in another table, establishing relationships between tables.
• Write a simple query to select all names from a customers table. SELECT Name FROM Customers;

Level Up: Intermediate Challenges

• How can you filter data based on specific conditions? Use the WHERE clause to specify conditions for selecting rows. Operators like =, >, <, LIKE, and IN help filter data.
• Join tables with common columns. Explain the different types of joins (INNER, LEFT, RIGHT, FULL).Joins combine data from multiple tables based on shared columns. INNER JOIN returns rows where the join condition is met in both tables. LEFT JOIN includes all rows from the left table and matching rows from the right table. RIGHT JOIN includes all rows from the right table and matching rows from the left table. FULL JOIN includes all rows from both tables, even if there's no match in the other table.
• Write a query to find the total number of orders placed by each customer in the last month. Use GROUP BY to group rows based on a column and aggregate functions like COUNT to calculate totals per group.

Advanced Arena: Mastering Complexities

• Explain the concept of subqueries and nested subqueries. Subqueries are embedded queries used within another query to filter or manipulate data. Nested subqueries involve subqueries within subqueries.
• How can you handle NULL values in your queries? Use functions like ISNULL or COALESCE to check for NULL values and provide alternative values.
• Write a query to find the top 10 customers with the highest total order amounts. Use ORDER BY to sort data and LIMIT (or TOP in some dialects) to restrict the number of returned rows.

Bonus Round: Exploring Additional Concepts

• What are views in SQL? How do they differ from tables? Views are virtual tables based on underlying tables but don't store data themselves. They offer a way to simplify complex queries and control data access.
• Explain the concept of transactions and their ACID properties (Atomicity, Consistency, Isolation, Durability). Transactions group multiple database operations to ensure data integrity. ACID properties guarantee the success or failure of an entire transaction.
• Describe some best practices for writing efficient and maintainable SQL queries. Emphasize proper use of indexes, avoiding unnecessary data retrieval, and writing clear and concise code.