[Solved] Identify the error in the following SQL set operation:SELECT id, name FROM CustomersUNIONSELECT customer_id FROM Orders; | SQL

SQL - Set Operations

Identify the error in the following SQL set operation:

SELECT id, name FROM Customers
UNION
SELECT customer_id FROM Orders;

AColumn names do not match between queries.

BUNION cannot be used with SELECT statements.

CData types of columns are incompatible.

DThe second query has fewer columns than the first.

Step-by-Step Solution

Solution:

Step 1: Compare column counts in both queries
The first query selects 2 columns (id, name), the second selects only 1 column (customer_id). This mismatch causes an error.
Step 2: Check other possible errors
Column names do not need to match, and UNION works with SELECT statements. Data types are unknown but column count mismatch is enough to cause error.
Final Answer:
The second query has fewer columns than the first. -> Option D
Quick Check:
Column count mismatch = B [OK]

Quick Trick: Ensure both queries select same number of columns [OK]

Common Mistakes:

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