WHERE Clause & Filtering

SELECT & Data Retrieval

CASE Statements & Conditional Logic

String Functions & Operations

Arithmetic & Numeric Functions

Write a query returning full_name, annual_salary, and monthly_salary for all employees — ORDER BY annual_salary DESC

Fix this query: SELECT price * 1.2 AS price_with_tax FROM products WHERE price_with_tax > 100

Build a product report with: subtotal, discount_amount (10%), net_amount, and tax_amount (8%) — all using ROUND()

Write a SARGable rewrite for: WHERE MONTH(order_date) = 3 AND YEAR(order_date) = 2024

Create a NULL-safe full_name expression that works on PostgreSQL, MySQL, and SQL Server

Write a JOIN query using table aliases for employees, departments, and locations — no ambiguous column names

Why can you use a column alias in ORDER BY but not in WHERE?

What is a non-SARGable predicate? Give an example and fix it.

How does NULL behave in || concatenation vs CONCAT()?

Can you use a SELECT alias in GROUP BY? Does it depend on the database?

What is operator precedence in SQL arithmetic? Give a formula that would be wrong without parentheses.

PostgreSQL docs: Value Expressions and Operator Precedence

SQL Server docs: Column Aliases (Transact-SQL)

MySQL docs: CONCAT() and String Functions

Use The Index, Luke: Sargable WHERE Clauses