How to Query MySQL for Restaurants with All Menu Items Over a Specified Price

Learn how to effectively query your `MySQL` database to retrieve restaurant names and their menu items where all items exceed a specified price, such as $10.
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This video is based on the question https://stackoverflow.com/q/74635425/ asked by the user 'Martin Zanony' ( https://stackoverflow.com/u/13350520/ ) and on the answer https://stackoverflow.com/a/74635506/ provided by the user 'Stephen Quan' ( https://stackoverflow.com/u/881441/ ) at 'Stack Overflow' website. Thanks to these great users and Stackexchange community for their contributions.

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Solving the MySQL Query Challenge: Finding Restaurants with All High-Priced Items

In the world of database management and SQL queries, it's not uncommon to face challenges when trying to extract specific information. One such challenge arises when you want to show restaurant names and their food items that are priced over a certain threshold. In this guide, we’ll walk through how to craft a MySQL query that addresses a situation where you need to ensure that all menu items for a restaurant exceed a specified price.

The Problem: Filtering Restaurants by Item Price

You have two tables in your MySQL database: restaurant and food_item. Your goal is to display the name of the restaurant, the item name, and the price of food items only when all items on the restaurant's menu have a price over $10.

Database Structure

Here’s a simple representation of your tables:

restaurant table

[[See Video to Reveal this Text or Code Snippet]]

food_item table

[[See Video to Reveal this Text or Code Snippet]]

The Challenge

Your initial SQL query can retrieve items priced over $10, but it does not filter out restaurants that have items on their menu priced at or below $10. The effective solution requires a strategic approach to exclude those restaurants entirely.

The Solution: Using NOT EXISTS

To solve this problem, we need to eliminate restaurants that have any food item priced at or below $10. This is achieved using a subquery combined with NOT EXISTS. Here’s how the final SQL query looks:

[[See Video to Reveal this Text or Code Snippet]]

Breakdown of the Query

SELECT Statement:

This section is straightforward. We’re selecting the restaurant name, food item name, and the price of the food item.

JOIN Clause:

You correctly use the JOIN clause to connect the restaurant and food_item tables based on their relationship (using restaurant.id and food_item.restaurant_id).

WHERE NOT EXISTS:

This is the key part. Here’s how it works:

The subquery checks for the existence of any food item that is priced at or below $10 for each restaurant.

If the subquery finds any such item, the restaurant is excluded from the results.

Curated Results:

After applying the NOT EXISTS condition, the remaining results will only include restaurants where all items are priced above $10.

Conclusion

Using the method outlined above, you can effectively filter your restaurant data to meet your criteria, ensuring you only retrieve those establishments that uphold a certain standard for their menu pricing. This approach not only clarifies your results but also enhances your database management strategies.

By mastering advanced SQL queries, you can harness the full potential of your relational database, making data retrieval both efficient and purposeful.

For more practical SQL tips and tricks, stay tuned for our upcoming posts!

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