[Solved] You wrote this query:SELECT A.Name, B.OrderID FROM Customers A LEFT JOIN Orders B ON A.ID = B.CustomerID WHERE B.OrderID > 100;But it returns no rows for customers without orders. Why? | SQL

SQL - LEFT and RIGHT JOIN

You wrote this query:
SELECT A.Name, B.OrderID FROM Customers A LEFT JOIN Orders B ON A.ID = B.CustomerID WHERE B.OrderID > 100;
But it returns no rows for customers without orders. Why?

AON condition is wrong

BThe WHERE clause filters out rows where B.OrderID is NULL

CCustomers table is empty

DLEFT JOIN syntax is incorrect

Step-by-Step Solution

Solution:

Step 1: Understand WHERE effect on LEFT JOIN
WHERE filters after join; condition B.OrderID > 100 excludes rows where B.OrderID is NULL.
Step 2: Result of filtering
Customers without orders have NULL OrderID, so they are removed by WHERE clause.
Final Answer:
The WHERE clause filters out rows where B.OrderID is NULL -> Option B
Quick Check:
WHERE on right table column removes NULL rows in LEFT JOIN [OK]

Quick Trick: Use WHERE on right table columns carefully with LEFT JOIN [OK]

Common Mistakes:

MISTAKES

Thinking LEFT JOIN always keeps all left rows
Ignoring WHERE clause effect
Assuming syntax error causes no rows

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You wrote this query:

Step 1: Understand WHERE effect on LEFT JOIN

Step 2: Result of filtering

Final Answer:

Quick Check:

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