Ordering and grouping in Laravel - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ component_behavior

intermediate

What is the output of this Laravel Eloquent query?

Consider the following Eloquent query in Laravel:

$results = User::select('role', DB::raw('count(*) as total'))
    ->groupBy('role')
    ->orderBy('total', 'desc')
    ->get();

return $results->toArray();

What does this query return?

Laravel

use Illuminate\Support\Facades\DB;

$results = User::select('role', DB::raw('count(*) as total'))
    ->groupBy('role')
    ->orderBy('total', 'desc')
    ->get();

return $results->toArray();

A A syntax error because 'total' cannot be used in orderBy after groupBy.

B An array of users ordered alphabetically by role name.

C An array of all users with a total count of all users appended to each record.

D An array of roles with their user counts, ordered from highest to lowest count.

💡 Hint

Think about what groupBy and orderBy do together in Eloquent queries.

The query groups users by their role, counts how many users each role has, and orders the results by that count descending. So the output is a list of roles with their user counts from highest to lowest.

📝 Syntax

intermediate

Which option correctly groups and orders users by status and creation date?

You want to group users by their 'status' and order each group by the earliest 'created_at' date ascending. Which Eloquent query is correct?

A

User::select('status', DB::raw('min(created_at) as earliest'))
    ->groupBy('status')
    ->orderBy('earliest', 'asc')
    ->get();

B User::orderBy('created_at', 'asc')->groupBy('status')->get();

C User::groupBy('status')->orderBy('created_at', 'asc')->get();

D User::groupBy('status')->orderByRaw('MIN(created_at) ASC')->get();

💡 Hint

Remember that ordering by an aggregate requires selecting it first.

Option A correctly selects the minimum created_at per status group, groups by status, and orders by that minimum date ascending. Other options either misuse orderBy or groupBy.

🔧 Debug

advanced

Why does this Laravel query throw an SQL error?

Given this Laravel query:

$users = User::select('status', DB::raw('count(*) as total'))
    ->orderBy('total', 'desc')
    ->groupBy('status')
    ->get();

It throws an SQL error about 'total' in ORDER BY. Why?

Laravel

use Illuminate\Support\Facades\DB;

$users = User::select('status', DB::raw('count(*) as total'))
    ->orderBy('total', 'desc')
    ->groupBy('status')
    ->get();

A Because 'total' is not a column in the users table, orderBy cannot use it.

B Because orderBy is called before groupBy, the alias 'total' is not recognized in ORDER BY.

C Because groupBy must come before select in the query chain.

D Because count(*) cannot be aliased in select when using groupBy.

💡 Hint

Think about the order SQL processes clauses and how Laravel builds the query.

In SQL, ORDER BY is processed after GROUP BY and SELECT. But Laravel builds the query in the order methods are called. Calling orderBy before groupBy causes the alias 'total' to be unknown at that point, causing an SQL error.

🧠 Conceptual

advanced

How does Laravel handle ordering by a computed column in a grouped query?

In Laravel Eloquent, when you group records and select a computed column like count(*), how can you order the results by that computed column?

A You can orderBy the computed column name directly without selecting it first.

B Laravel automatically orders grouped queries by the first selected column.

C You must select the computed column with an alias and then orderBy using that alias.

D You cannot order grouped queries by computed columns in Laravel.

💡 Hint

Think about how SQL requires ordering by columns present in the SELECT clause.

To order by a computed column in a grouped query, you must select it with an alias and then orderBy that alias. Otherwise, SQL will not recognize the column in ORDER BY.

❓ state_output

expert

What is the count of groups returned by this Laravel query?

Given the users table has 100 records with 4 distinct 'department' values, what is the count of items in the result of this query?

$groups = User::groupBy('department')->get();
return $groups->count();

Laravel

use App\Models\User;

$groups = User::groupBy('department')->get();
return $groups->count();

A 100

B 4

C 1

D 0

💡 Hint

Remember that groupBy alone does not reduce the number of rows returned without aggregation.

In Laravel, calling groupBy without selecting aggregates returns all rows, not grouped rows. So the count is the total number of records, 100, not the number of groups.