[Solved] Given the table students with columns class and name, what is the output of this query?SELECT class, ARRAY_AGG(name ORDER BY name) FROM students GROUP BY class ORDER BY class; | PostgreSQL

PostgreSQL - Aggregate Functions and GROUP BY

Given the table students with columns class and name, what is the output of this query?

SELECT class, ARRAY_AGG(name ORDER BY name) FROM students GROUP BY class ORDER BY class;

A[{class: '1A', array_agg: ['Alice']}, {class: '2B', array_agg: ['Charlie', 'David', 'Bob']}]

B[{class: '1A', array_agg: ['Bob', 'Alice']}, {class: '2B', array_agg: ['David', 'Charlie']}]

C[{class: '1A', array_agg: ['Alice', 'Charlie']}, {class: '2B', array_agg: ['Bob', 'David']}]

D[{class: '1A', array_agg: ['Alice', 'Bob']}, {class: '2B', array_agg: ['Charlie', 'David']}]

Step-by-Step Solution

Solution:

Step 1: Understand GROUP BY and ARRAY_AGG with ORDER BY
The query groups rows by class and collects names into arrays sorted alphabetically.
Step 2: Analyze the ordering inside ARRAY_AGG
Names inside each class array are sorted ascending, so 'Alice' comes before 'Bob' in '1A', and 'Charlie' before 'David' in '2B'.
Final Answer:
[{class: '1A', array_agg: ['Alice', 'Bob']}, {class: '2B', array_agg: ['Charlie', 'David']}] -> Option D
Quick Check:
ARRAY_AGG with ORDER BY sorts array elements [OK]

Quick Trick: ARRAY_AGG(... ORDER BY ...) sorts array elements [OK]

Common Mistakes:

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Given the table students with columns class and name, what is the output of this query?