[Solved] Which of the following is the correct syntax for using a subquery in the FROM clause in PostgreSQL? — Ans: SELECT * FROM (SELECT id FROM users) AS sub; | PostgreSQL

PostgreSQL - Subqueries in PostgreSQL

Which of the following is the correct syntax for using a subquery in the FROM clause in PostgreSQL?

ASELECT * FROM (SELECT id FROM users) AS sub;

BSELECT * FROM users WHERE (SELECT id FROM users);

CSELECT * FROM users JOIN (SELECT id FROM users);

DSELECT * FROM users (SELECT id FROM users) AS sub;

Step-by-Step Solution

Solution:

Step 1: Identify correct subquery syntax in FROM
The subquery must be enclosed in parentheses and given an alias using AS.
Step 2: Check each option
SELECT * FROM (SELECT id FROM users) AS sub; correctly uses parentheses and alias. Others either misuse WHERE, JOIN without ON, or lack alias.
Final Answer:
SELECT * FROM (SELECT id FROM users) AS sub; -> Option A
Quick Check:
Subquery in FROM needs parentheses + alias [OK]

Quick Trick: Always alias subqueries in FROM with AS [OK]

Common Mistakes:

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Which of the following is the correct syntax for using a subquery in the FROM clause in PostgreSQL?