学ぶ Subqueries in SELECT and WHERE Clauses | Subqueries in E-commerce Analytics

メニューを表示するにはスワイプしてください


              123456789
            
SELECT
    p.product_id,
    p.name,
    (
        SELECT COUNT(*)
        FROM orders o
        WHERE o.product_id = p.product_id
    ) AS total_orders
FROM products p;

This query demonstrates how to use a subquery within the SELECT clause. The main query retrieves each product's ID and name from the products table. For each product, the subquery calculates the total number of orders by counting rows in the orders table where the product_id matches the current product. The result is a list of products, each with its total order count. This technique allows you to include calculated or aggregated data for each row in your result set, using subqueries that reference the current row's values.


              12345678
            
SELECT DISTINCT c.customer_id, c.name
FROM customers c
WHERE c.customer_id IN (
    SELECT o.customer_id
    FROM orders o
    JOIN products p ON o.product_id = p.product_id
    WHERE p.category = 'Electronics'
);

1. Which statement best describes the difference between using a subquery in the SELECT clause and in the WHERE clause?

2. Fill in the blanks to select product names from the `products` table that have been ordered at least once.

すべて明確でしたか？

フィードバックありがとうございます！

セクション 1. 章 2

AIに質問する

何でも質問するか、提案された質問の1つを試してチャットを始めてください

セクション 1. 章 2

Subqueries in SELECT and WHERE Clauses

1. Which statement best describes the difference between using a subquery in the SELECT clause and in the WHERE clause?

2. Fill in the blanks to select product names from the products table that have been ordered at least once.

2. Fill in the blanks to select product names from the `products` table that have been ordered at least once.