SQL - LEFT and RIGHT JOIN
Given tables Employees (id, name) and Sales (emp_id, amount), what will this query return?
SELECT Employees.name, Sales.amount FROM Employees LEFT OUTER JOIN Sales ON Employees.id = Sales.emp_id;
Given tables Employees (id, name) and Sales (emp_id, amount), what will this query return? SELECT Employees.name, Sales.amount FROM Employees LEFT OUTER JOIN Sales ON Employees.id = Sales.emp_id;
medium📝 query result Q4 of 15
Step-by-Step Solution
Solution:
Step 1: Analyze LEFT OUTER JOIN effect
LEFT OUTER JOIN keeps all rows from Employees and matches Sales; unmatched Sales show NULL.Step 2: Understand result columns
Employees.name always present; Sales.amount NULL if no matching sale.Final Answer:
All employees with their sales amounts; NULL if no sales -> Option DQuick Check:
LEFT OUTER JOIN returns all left rows with NULLs for unmatched right [OK]
Quick Trick: LEFT OUTER JOIN keeps all left table rows with NULLs for no match [OK]
Common Mistakes:
MISTAKES- Expecting only matched rows
- Confusing left and right table roles
- Assuming NULLs are filtered out
Master "LEFT and RIGHT JOIN" in SQL
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