SQL Practical Exam -- Sample Project

This exam is to practice SQL skills to get ready and prepare for Data Engineer certification provided by DataCamp. The exam covered variety of of real-world SQL tasks, focusing on data cleaning, database querying, and aggregation.

Overview

The exam was divided into three tasks, each assessing different SQL skills.

Task 1 – Data Cleaning and Type Conversion

• String Manipulation:
  • Cleaned categorical and text data using functions such as TRIM(), LOWER(), UPPER(), and REPLACE().
    
  • Removed unwanted characters and standardized text formats.
• Data Type Conversion:
  • Used casting functions (CAST(), CONVERT()) to change values between numeric, text, and date formats.
    
  • Ensured compatibility for further calculations and joins.

Task 2 – Schema Interpretation and Table Combination

• Database Schema Understanding:
  • Read and interpreted the schema to understand relationships between tables.
    
  • Identified primary keys, foreign keys, and data types for correct joins.
• Combining Data:
  • Used JOIN operations (INNER, LEFT) to combine data by columns.
    
  • Applied UNION and UNION ALL to merge data by rows where applicable.

Task 3 – Data Aggregation

• Numeric Aggregation:
  • Calculated SUM(), AVG(), MIN(), and MAX() for numerical columns.
• Categorical Aggregation:
  • Counted distinct values and grouped results using GROUP BY.
• Date Aggregation:
  • Extracted and aggregated data based on YEAR(), MONTH(), and DAY() functions.

License

This project is for educational purposes only, based on a DataCamp sample SQL practical exam.