Which of the following best describes the result of a FULL OUTER JOIN when there are no matching rows between the two tables?

easy📝 Conceptual Q2 of 15

PostgreSQL - Joins in PostgreSQL

Which of the following best describes the result of a FULL OUTER JOIN when there are no matching rows between the two tables?

AThe result will be empty

BThe result will contain all rows from both tables with NULLs in unmatched columns

CThe result will contain only rows from the left table

DThe result will contain only rows from the right table

Step-by-Step Solution

Solution:

Step 1: Consider no matching rows scenario
If no rows match between tables, FULL OUTER JOIN still returns all rows from both tables.
Step 2: Understand NULL filling
Columns from the opposite table will be NULL where no match exists.
Final Answer:
The result will contain all rows from both tables with NULLs in unmatched columns -> Option B
Quick Check:
No matches means all rows with NULLs = C [OK]

Quick Trick: FULL OUTER JOIN never returns empty if tables have rows [OK]

Common Mistakes:

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