[Solved] Consider this SQL query:SELECT name FROM employees UNION SELECT name, department FROM managers;What is the issue with this query? | SQL

SQL - Set Operations

Consider this SQL query:
SELECT name FROM employees UNION SELECT name, department FROM managers;
What is the issue with this query?

AThe number of columns in both SELECT statements differ

BUNION cannot be used with SELECT statements

CThe query will return duplicate rows

DThe query is missing a WHERE clause

Step-by-Step Solution

Solution:

Step 1: Check column counts in SELECTs
The first SELECT returns 1 column (name), the second returns 2 columns (name, department).
Step 2: Understand UNION column rules
UNION requires all SELECT statements to have the same number of columns with compatible types.
Final Answer:
The number of columns in both SELECT statements differ -> Option A
Quick Check:
UNION needs same columns = C [OK]

Quick Trick: UNION needs same column count in all SELECTs [OK]

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