Day 23 of My Data Analytics Journey !

Today was a productive day in my Data Analytics learning! Here’s what I learned and practiced:

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📚 Topics Learned

• UNION vs UNION ALL

  • UNION → Combines results of two queries and removes duplicates.
  • UNION ALL → Combines results of two queries without removing duplicates.

• Constraints in SQL

  • NOT NULL → Ensures a column cannot have NULL values.
  • DEFAULT → Provides a default value for a column if none is specified.
  • PRIMARY KEY → Unique identifier for each record (only one per table).
  • FOREIGN KEY → Maintains referential integrity between two tables.
  • UNIQUE → Ensures all values in a column are unique.
  • INDEX → Improves query performance on large datasets.

• Timestamps

  • CURRENT_TIMESTAMP → Stores the current date & time.
  • DEFAULT CURRENT_TIMESTAMP → Auto-assigns the current timestamp when inserting data.

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📝 Tasks Completed

1. Extracted names from the movie table with two same letters in the same place.
2. Found actors who acted in all movies.
3. Company Database Queries:

• ✅ Employee and their Manager (both in employee table).
• ✅ Get project names of each employee (employee + employee_project + projects).
• ✅ Department-wise employee count (departments + employee).
• ✅ Show each project with its budget and total salaries of employees assigned (projects + employee_project + employees).
• ✅ Find employees whose department is the same as their manager’s department.
• ✅ List employees who are not working on any project (employee_project + employee).
• ✅ Find the manager with the most employees reporting to them.

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💡 Key Takeaway

Learning UNION, constraints, and advanced SQL joins helped me understand how to manage relational databases better. Today’s hands-on tasks gave me confidence in writing queries for *real-world business use *