[Solved] Find the problem in this query:SELECT id, name FROM staff UNION SELECT id, salary FROM payroll; — Ans: Data types of the second columns differ and are incompatible. | SQL

SQL - Set Operations

Find the problem in this query:
SELECT id, name FROM staff UNION SELECT id, salary FROM payroll;

AColumn names must be the same in both SELECT statements.

BUNION cannot combine columns with different names.

CData types of the second columns differ and are incompatible.

DBoth SELECT statements must have ORDER BY clauses.

Step-by-Step Solution

Solution:

Step 1: Compare columns in both SELECTs
Both have 2 columns, but second columns are 'name' (likely VARCHAR) and 'salary' (likely numeric).
Step 2: Check data type compatibility
Different data types in same column position cause error in UNION.
Final Answer:
Data types of the second columns differ and are incompatible. -> Option C
Quick Check:
Data type mismatch error = B [OK]

Quick Trick: UNION columns must have compatible data types [OK]

Common Mistakes:

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