[Solved] Which condition must be true for two SELECT statements to be combined using UNION in SQL? — Ans: Both SELECT statements must have the same number of columns with compatible... | SQL

SQL - Set Operations

Which condition must be true for two SELECT statements to be combined using UNION in SQL?

ABoth SELECT statements must have identical column names.

BBoth SELECT statements must have the same number of columns with compatible data types.

CBoth SELECT statements must use the same WHERE clause.

DBoth SELECT statements must select from the same table.

Step-by-Step Solution

Solution:

Step 1: Understand the requirement for UNION
UNION combines results vertically, so columns must match in number and type.
Step 2: Check each option against the rule
Only Both SELECT statements must have the same number of columns with compatible data types. states the correct rule about column count and compatible types.
Final Answer:
Both SELECT statements must have the same number of columns with compatible data types. -> Option B
Quick Check:
Set operation column matching = D [OK]

Quick Trick: UNION needs same column count and compatible types [OK]

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Which condition must be true for two SELECT statements to be combined using UNION in SQL?