SQL Skills Library

Easy

• Introduction to SQL and databases
• SELECT, FROM, and WHERE basics
• Sorting results with ORDER BY
• Filtering with AND, OR, IN, BETWEEN, and LIKE
• Writing readable queries (formatting and aliases)
• SQL vs Excel: when to use which

Intermediate

• Aggregate functions (COUNT, SUM, AVG, MIN, MAX)
• GROUP BY and HAVING
• JOINs explained (INNER, LEFT, RIGHT, FULL)
• Finding duplicates in a table
• NULL values and how to handle them
• CASE statements (SQL’s version of IF)
• Date functions
• INSERT, UPDATE, and DELETE

Advanced

• Subqueries
• Common Table Expressions (CTEs)
• Window functions
• Views and stored procedures
• Indexes and query performance