[Solved] Find the issue in this JOIN query:SELECT o.id FROM orders o JOIN customers c ON o.customer_id = c.customer_id WHERE c.... | SQL

SQL - Subqueries

Find the issue in this JOIN query:

SELECT o.id FROM orders o JOIN customers c ON o.customer_id = c.customer_id WHERE c.status = 'active';
Given that the customers table's primary key is id, not customer_id.

AThe JOIN condition uses a wrong column name causing no matches.

BThe WHERE clause is incorrect syntax.

CThe query should use a subquery instead of JOIN.

DThe SELECT clause is missing table aliases.

Step-by-Step Solution

Solution:

Step 1: Check JOIN condition
The JOIN uses c.customer_id, but the correct column is c.id.
Step 2: Understand effect of wrong column
Using a wrong column causes no matching rows, resulting in empty or incorrect output.
Final Answer:
The JOIN condition uses a wrong column name causing no matches. -> Option A
Quick Check:
Correct JOIN keys = correct output [OK]

Quick Trick: Always verify JOIN keys match primary/foreign keys [OK]

Common Mistakes:

MISTAKES

Using incorrect column names in JOIN
Assuming WHERE clause errors cause no output
Ignoring table schema details

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More SQL Quizzes

Find the issue in this JOIN query:

Step 1: Check JOIN condition

Step 2: Understand effect of wrong column

Final Answer:

Quick Check:

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