Aggregates (count, sum, avg) in Laravel - Cheat Sheet & Quick Revision

Recall & Review

beginner

What does the count() aggregate function do in Laravel?

It counts the number of records in a database table or query result.

beginner

How do you calculate the sum of a column using Laravel's query builder?

Use the sum('column_name') method to add all values in that column.

beginner

What is the purpose of the avg() method in Laravel?

It calculates the average (mean) value of a specified column in the database.

beginner

Show a simple example of using count() in Laravel's query builder.

Example: <br>$totalUsers = DB::table('users')->count();<br>This counts all users in the 'users' table.

intermediate

Can you chain aggregate functions with other query builder methods in Laravel?

Yes, you can add conditions before calling aggregates, like:<br>$sum = DB::table('orders')->where('status', 'paid')->sum('amount');

Which Laravel method counts the number of rows in a table?

A total()

B count()

C avg()

D sum()

The count() method returns the number of rows.

How do you get the total sum of a column named 'price' in Laravel?

A DB::table('items')->total('price')

B DB::table('items')->count('price')

C DB::table('items')->avg('price')

D DB::table('items')->sum('price')

Use sum('price') to add all values in the 'price' column.

What does avg('score') return in Laravel?

A The average score

B The highest score

C The total score

D The number of scores

avg('score') calculates the average value of the 'score' column.

Can you add a where condition before using sum()?

A No, aggregates don't support conditions

B Only with <code>count()</code>

C Yes, you can chain <code>where</code> before <code>sum()</code>

D Only with <code>avg()</code>

You can chain where to filter records before summing.

Which aggregate method would you use to find how many orders are in the database?

A count()

B avg()

C sum()

D max()

count() returns the number of orders.

Explain how to use Laravel's aggregate functions to get the total number of users, the sum of their balances, and the average age.

Think about chaining methods on the DB facade with the right aggregate functions.

Describe a real-life scenario where you would use the sum() and avg() aggregates in a Laravel application.

Imagine a store or review system needing totals and averages.