[Solved] Given the ENUM type and table:CREATE TYPE mood AS ENUM ('happy', 'sad', 'neutral');... SELECT * FROM person WHERE current_mood = 'neutral';What will the SELECT query return? | PostgreSQL

PostgreSQL - Advanced Features

Given the ENUM type and table:

CREATE TYPE mood AS ENUM ('happy', 'sad', 'neutral');
CREATE TABLE person (name TEXT, current_mood mood);
INSERT INTO person VALUES ('Alice', 'happy'), ('Bob', 'sad');
SELECT * FROM person WHERE current_mood = 'neutral';

What will the SELECT query return?

ARows with persons having mood 'happy' or 'sad'

BRows with all persons, ignoring mood

CError because 'neutral' is not a valid ENUM value

DNo rows, because no person has mood 'neutral'

Step-by-Step Solution

Solution:

Step 1: Understand inserted data
Only 'happy' and 'sad' moods are inserted; no 'neutral' rows exist.
Step 2: Analyze SELECT query
Query filters for current_mood = 'neutral', which matches no rows.
Final Answer:
No rows, because no person has mood 'neutral' -> Option D
Quick Check:
Query result = empty set when no matching ENUM value rows [OK]

Quick Trick: Query returns no rows if no matching ENUM value exists [OK]

Common Mistakes:

Assuming query returns error for valid ENUM value
Expecting all rows returned without filter
Confusing ENUM values with strings not in ENUM

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Given the ENUM type and table:

Step 1: Understand inserted data

Step 2: Analyze SELECT query

Final Answer:

Quick Check:

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