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LeetCode SQL 50 Solution/1484. Group Sold Products By The Date/readme.md

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+Here’s a well-structured `README.md` for **LeetCode 1484 - Group Sold Products By The Date**, formatted for a GitHub repository: 
+
+```md
+# 🛍️ Group Sold Products By The Date - LeetCode 1484
+
+## 📌 Problem Statement
+You are given a table **Activities** that contains records of products sold on different dates.
+
+Your task is to return:
+- The **number of distinct products** sold on each date.
+- A **comma-separated string** of the product names, sorted **lexicographically**.
+
+The result should be **ordered by `sell_date`**.
+
+---
+
+## 📊 Table Structure
+
+### **Activities Table**
+| Column Name | Type |
+| ----------- | ------- |
+| sell_date | date |
+| product | varchar |
+
+- This table **does not** have a **primary key**.
+- It may **contain duplicate entries**.
+
+---
+
+## 📊 Example 1:
+### **Input:**
+#### **Activities Table**
+| sell_date | product |
+| ---------- | ---------- |
+| 2020-05-30 | Headphone |
+| 2020-06-01 | Pencil |
+| 2020-06-02 | Mask |
+| 2020-05-30 | Basketball |
+| 2020-06-01 | Bible |
+| 2020-06-02 | Mask |
+| 2020-05-30 | T-Shirt |
+
+### **Output:**
+| sell_date | num_sold | products |
+| ---------- | -------- | ---------------------------- |
+| 2020-05-30 | 3 | Basketball,Headphone,T-Shirt |
+| 2020-06-01 | 2 | Bible,Pencil |
+| 2020-06-02 | 1 | Mask |
+
+### **Explanation:**
+- `2020-05-30`: Sold items → _(Headphone, Basketball, T-Shirt)_ 
+ - Sorted → **"Basketball, Headphone, T-Shirt"** 
+- `2020-06-01`: Sold items → _(Pencil, Bible)_ 
+ - Sorted → **"Bible, Pencil"** 
+- `2020-06-02`: Sold item → _(Mask)_ 
+ - **"Mask"** (only one item)
+
+---
+
+## 🖥 SQL Solution
+
+### ✅ **Using `GROUP_CONCAT` with `DISTINCT`**
+#### **Explanation:**
+- Use `COUNT(DISTINCT product)` to get the **number of distinct products**.
+- Use `GROUP_CONCAT(DISTINCT product ORDER BY product ASC)` to **join product names in alphabetical order**.
+- Group by `sell_date`, then order the result by `sell_date`.
+
+```sql
+SELECT 
+ sell_date, 
+ COUNT(DISTINCT product) AS num_sold,
+ GROUP_CONCAT(DISTINCT product ORDER BY product ASC SEPARATOR ',') AS products
+FROM Activities
+GROUP BY sell_date
+ORDER BY sell_date ASC;
+```
+
+---
+
+## 🐍 Pandas Solution (Python)
+#### **Explanation:**
+- **Group by `sell_date`**.
+- Use `.nunique()` to count distinct products.
+- Use `', '.join(sorted(set(products)))` to sort and concatenate product names.
+
+```python
+import pandas as pd
+
+def group_sold_products(activities: pd.DataFrame) -> pd.DataFrame:
+ grouped_df = (
+ activities.groupby("sell_date")["product"]
+ .agg(lambda x: ", ".join(sorted(set(x))))
+ .reset_index()
+ )
+ grouped_df["num_sold"] = grouped_df["product"].apply(lambda x: len(x.split(",")))
+ return grouped_df.rename(columns={"product": "products"})
+```
+
+---
+
+## 📁 File Structure
+```
+📂 Group-Sold-Products
+│── 📜 README.md
+│── 📜 solution.sql
+│── 📜 solution_pandas.py
+│── 📜 test_cases.sql
+```
+
+---
+
+## 🔗 Useful Links
+- 📖 [LeetCode Problem](https://leetcode.com/problems/group-sold-products-by-the-date/)
+- 📚 [SQL `GROUP BY`](https://www.w3schools.com/sql/sql_groupby.asp)
+- 🐍 [Pandas `groupby()` Documentation](https://pandas.pydata.org/pandas-docs/stable/reference/api/pandas.DataFrame.groupby.html)
+```
+
+### Features of this `README.md`:
+✅ **Clear problem statement with tables** 
+✅ **Example with step-by-step explanation** 
+✅ **SQL and Pandas solutions with detailed breakdowns** 
+✅ **File structure for easy organization** 
+✅ **Helpful references for further learning** 
+
+Would you like any modifications? 🚀