Welcome to

Sara's SQL Trainer

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🗃️

Your Tables

🎯

Your Mission

💼 Why is this useful?

✨ Target Result


                        

                    

                    

                        
                        
                        
                    

                

            


            

                

                    💻
                    
Write Your Magic Query

                

                
                

                    
                    
                    
                

                
                
                

            


            

                

                    📊
                    
Your Amazing Result

                

                

            


            

                

                    📖
                    
Your SQL Toolkit

                    Keep this handy!
                

                

                    

                        
SELECT

                        
Select columns from a table

                        SELECT name FROM users
                        SELECT * FROM products
                        -- * means all columns
                    

                    

                        
WHERE

                        
Filter rows with conditions

                        WHERE price > 100
                        WHERE name = 'Alice'
                        WHERE name LIKE 'A%'
                    

                    

                        
ORDER BY

                        
Sort results

                        ORDER BY name ASC
                        ORDER BY price DESC
                    

                    

                        
🔗 JOIN Types

                        
Combine data from multiple tables

                        

                            

                                
INNER JOIN

                                
Returns only matching rows from both tables

                                SELECT * FROM A INNER JOIN B ON A.id = B.a_id
                            

                            

                                
LEFT JOIN

                                
All rows from left table + matching from right

                                SELECT * FROM A LEFT JOIN B ON A.id = B.a_id
                            

                            

                                
RIGHT JOIN

                                
All rows from right table + matching from left

                                SELECT * FROM A RIGHT JOIN B ON A.id = B.a_id
                            

                            

                                
FULL OUTER JOIN

                                
All rows from both tables

                                SELECT * FROM A FULL OUTER JOIN B ON A.id = B.a_id
                            

                        

                    

                    

                        
GROUP BY

                        
Group for aggregation

                        GROUP BY department
                        HAVING COUNT(*) > 2
                    

                    

                        
Aggregate

                        
Calculate values

                        COUNT(*), SUM(col)
                        AVG(col), MIN(col)
                    

                

            


            
            

                

                    ⚠️
                    
Common Mistakes to Avoid

                

                

                    

                        
❌ Missing Quotes

                        
Strings need single quotes

                        WHERE name = Alice
                        WHERE name = 'Alice'
                    

                    

                        
❌ WHERE + Aggregate

                        
Use HAVING, not WHERE for groups

                        WHERE COUNT(*) > 2
                        HAVING COUNT(*) > 2
                    

                    

                        
❌ SELECT not in GROUP BY

                        
Only select grouped or aggregate cols

                        SELECT name, dept GROUP BY dept
                        SELECT dept, COUNT(*) GROUP BY dept
                    

                    

                        
❌ JOIN without ON

                        
JOIN needs ON to connect tables

                        SELECT * FROM orders JOIN customers
                        JOIN customers ON orders.cust_id = customers.id
                    

                    

                        
❌ Missing Table Name

                        
FROM needs a table name

                        SELECT * FROM
                        SELECT * FROM employees
                    

                    

                        
❌ Typos in Keywords

                        
Check spelling carefully

                        SELEC * FROM table
                        SELECT * FROM table
                    

                    

                        
❌ ORDER BY Position

                        
ORDER BY comes after GROUP BY

                        ORDER BY col GROUP BY col2
                        GROUP BY col2 ORDER BY col
                    

                    

                        
❌ LIKE with =

                        
Use LIKE for patterns

                        WHERE name = 'A%'
                        WHERE name LIKE 'A%'
                    

                

            

        


        

        

            
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