[Solved] What is the main difference between a FULL OUTER JOIN and a LEFT JOIN in PostgreSQL? — Ans: FULL OUTER JOIN returns all rows from both tables, LEFT JOIN returns all rows... | PostgreSQL

PostgreSQL - Joins in PostgreSQL

What is the main difference between a FULL OUTER JOIN and a LEFT JOIN in PostgreSQL?

AFULL OUTER JOIN returns rows with NULLs removed, LEFT JOIN returns rows with NULLs included

BFULL OUTER JOIN returns only matching rows, LEFT JOIN returns all rows from both tables

CFULL OUTER JOIN returns only rows from the right table, LEFT JOIN returns only rows from the left table

DFULL OUTER JOIN returns all rows from both tables, LEFT JOIN returns all rows from the left table only

Step-by-Step Solution

Solution:

Step 1: Understand LEFT JOIN behavior
LEFT JOIN returns all rows from the left table and matching rows from the right table. If no match, right side columns are NULL.
Step 2: Understand FULL OUTER JOIN behavior
FULL OUTER JOIN returns all rows from both tables. If no match, NULLs fill missing side columns.
Final Answer:
FULL OUTER JOIN returns all rows from both tables, LEFT JOIN returns all rows from the left table only -> Option D
Quick Check:
JOIN type difference = A [OK]

Quick Trick: FULL OUTER JOIN keeps all rows from both tables [OK]

Common Mistakes:

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What is the main difference between a FULL OUTER JOIN and a LEFT JOIN in PostgreSQL?