📚 Learning Objectives Overview

• Determine when to use databases vs spreadsheets

• Extract data subsets by selecting specific columns

• Filter rows based on conditions using WHERE clauses

• Combine multiple conditions with AND/OR operators

• Use the IN operator for multiple value matching

🧠 Key Concepts Summary

1. Basic SELECT Syntax

SELECT column1, column2, column3
FROM database.table;

• Purpose: Extract specific columns from a table

• Key Point: List column names separated by commas

• Pro Tip: Use SELECT * to select ALL columns

2. WHERE Clause for Filtering

SELECT *
FROM database.table
WHERE condition;

• Purpose: Filter rows based on specific conditions

• Operators: <, >, =, <=, >=, !=

• Key Point: WHERE comes after FROM

3. Combining Conditions with AND/OR

WHERE condition1 AND condition2  -- Both must be true
WHERE condition1 OR condition2   -- Either can be true

• AND: Narrows results (more restrictive)

• OR: Broadens results (less restrictive)

• Pro Tip: Use parentheses for complex conditions

4. IN Operator for Multiple Values

WHERE column IN ('value1', 'value2', 'value3')

• Purpose: Check if value matches ANY in the list

• Better than: Multiple OR statements

• Remember: Values in parentheses, separated by commas

5. SQL vs Spreadsheets Advantages

1. Capacity: Handles larger datasets

2. Performance: Faster processing

3. Security: Better data protection

4. Integration: Works with other software

🎯 Memory Aids & Mnemonics

SFWO - SQL Query Order

SELECT → FROM → WHERE → Order matters!

Filter Operators Cheat Sheet

• < Less than (Left pointing = Less)

• > Greater than (Right pointing = gReater)

• = Exactly equals (single = for SQL)

• AND = All conditions (AND = All)

• OR = Optional conditions (OR = Optional)

IN Operator Memory Trick

"IN the club" - checking if someone is IN a list of members

💪 Practice Questions

Level 1: Basic SELECT

1. Write a query to select only the price column from flights.Flights

2. Select all columns from the flights table

3. Select d_from, d_to, and distance columns

Level 2: Simple WHERE

4. Find all flights with price greater than 250

5. Find all flights departing from 'Chicago'

6. Find all flights with distance less than 1000

Level 3: AND/OR Combinations

7. Find flights from Detroit with price under 150

8. Find flights to New York OR Los Angeles

9. Find flights from Chicago to Los Angeles with price under 200

Level 4: Complex Queries

10. Find all flights from Detroit OR Chicago with price between 100 and 200

11. Use IN to find flights going to Tokyo, Sydney, or Honolulu

12. Select specific columns for flights from Los Angeles to multiple Asian destinations

✅ Quick Reference Card

Essential SQL Keywords

• SELECT: Choose columns

• FROM: Specify table

• WHERE: Filter rows

• AND: Both conditions

• OR: Either condition

• IN: Match list values

Common Patterns

-- Pattern 1: Select specific columns
SELECT col1, col2 FROM table;

-- Pattern 2: Filter with single condition
SELECT * FROM table WHERE col = 'value';

-- Pattern 3: Multiple conditions
SELECT * FROM table WHERE col1 = 'A' AND col2 < 100;

-- Pattern 4: Either/or conditions
SELECT * FROM table WHERE col = 'A' OR col = 'B';

-- Pattern 5: Match multiple values
SELECT * FROM table WHERE col IN ('A', 'B', 'C');

🔄 Review Exercises

Scenario-Based Problems

Budget Traveler A client has $175 to spend and wants to fly from Detroit. Write a query to find suitable flights.

Flexible Destination A Chicago resident wants to visit either Miami, Orlando, or Atlanta. Show flight number, destination, and price.

Multi-City Search Find all flights under $200 departing from New York, Boston, or Philadelphia.

📝 Common Mistakes to Avoid

1. Forgetting semicolon at end of query

2. Wrong quote types - use single quotes for text values

3. Missing WHERE keyword before conditions

4. Incorrect AND/OR logic - use parentheses for clarity

5. Case sensitivity - be consistent with table/column names

🎓 Self-Assessment Checklist

• [ ] I can write a basic SELECT statement

• [ ] I can select all columns using *

• [ ] I can filter rows with WHERE

• [ ] I can use comparison operators (<, >, =)

• [ ] I can combine conditions with AND

• [ ] I can use OR for alternative conditions

• [ ] I can use IN for multiple value matching

• [ ] I understand when to use parentheses

• [ ] I know advantages of SQL over spreadsheets

• [ ] I can write queries for real-world scenarios

💡 Study Tips

1. Practice typing queries - syntax matters!

2. Start simple - one condition at a time

3. Test incrementally - add complexity gradually

4. Read error messages - they guide you

5. Draw diagrams - visualize your filters

6. Create flashcards for operators

7. Practice daily - 15 minutes makes perfect

🚀 Next Steps

After mastering these basics:

1. Learn about sorting with ORDER BY

2. Explore grouping with GROUP BY

3. Study aggregate functions (COUNT, SUM, AVG)

4. Practice joining multiple tables

5. Understand database design principles