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| 1 | +Here’s a well-structured `README.md` for **LeetCode 1327 - List the Products Ordered in a Period**, formatted for a GitHub repository: |
| 2 | + |
| 3 | +```md |
| 4 | +# 🛒 List the Products Ordered in a Period - LeetCode 1327 |
| 5 | + |
| 6 | +## 📌 Problem Statement |
| 7 | +You are given two tables: **Products** and **Orders**. |
| 8 | +Your task is to **list the product names** that had at least **100 units ordered in February 2020** along with the total amount ordered. |
| 9 | + |
| 10 | +--- |
| 11 | + |
| 12 | +## 📊 Table Structure |
| 13 | + |
| 14 | +### **Products Table** |
| 15 | +| Column Name | Type | |
| 16 | +| ---------------- | ------- | |
| 17 | +| product_id | int | |
| 18 | +| product_name | varchar | |
| 19 | +| product_category | varchar | |
| 20 | + |
| 21 | +- `product_id` is the **primary key** (unique identifier). |
| 22 | +- This table contains details about products. |
| 23 | + |
| 24 | +--- |
| 25 | + |
| 26 | +### **Orders Table** |
| 27 | +| Column Name | Type | |
| 28 | +| ----------- | ---- | |
| 29 | +| product_id | int | |
| 30 | +| order_date | date | |
| 31 | +| unit | int | |
| 32 | + |
| 33 | +- `product_id` is a **foreign key** referencing the `Products` table. |
| 34 | +- `order_date` represents when the order was placed. |
| 35 | +- `unit` represents the **number of products ordered** on that date. |
| 36 | +- The table **may contain duplicate rows**. |
| 37 | + |
| 38 | +--- |
| 39 | + |
| 40 | +## 🔢 Goal: |
| 41 | +Find all products that had **at least 100 units ordered** during **February 2020** and display: |
| 42 | +- `product_name` |
| 43 | +- Total `unit` ordered in that period |
| 44 | + |
| 45 | +--- |
| 46 | + |
| 47 | +## 📊 Example 1: |
| 48 | +### **Input:** |
| 49 | +#### **Products Table** |
| 50 | +| product_id | product_name | product_category | |
| 51 | +| ---------- | --------------------- | ---------------- | |
| 52 | +| 1 | Leetcode Solutions | Book | |
| 53 | +| 2 | Jewels of Stringology | Book | |
| 54 | +| 3 | HP | Laptop | |
| 55 | +| 4 | Lenovo | Laptop | |
| 56 | +| 5 | Leetcode Kit | T-shirt | |
| 57 | + |
| 58 | +#### **Orders Table** |
| 59 | +| product_id | order_date | unit | |
| 60 | +| ---------- | ---------- | ---- | |
| 61 | +| 1 | 2020-02-05 | 60 | |
| 62 | +| 1 | 2020-02-10 | 70 | |
| 63 | +| 2 | 2020-01-18 | 30 | |
| 64 | +| 2 | 2020-02-11 | 80 | |
| 65 | +| 3 | 2020-02-17 | 2 | |
| 66 | +| 3 | 2020-02-24 | 3 | |
| 67 | +| 4 | 2020-03-01 | 20 | |
| 68 | +| 4 | 2020-03-04 | 30 | |
| 69 | +| 4 | 2020-03-04 | 60 | |
| 70 | +| 5 | 2020-02-25 | 50 | |
| 71 | +| 5 | 2020-02-27 | 50 | |
| 72 | +| 5 | 2020-03-01 | 50 | |
| 73 | + |
| 74 | +### **Output:** |
| 75 | +| product_name | unit | |
| 76 | +| ------------------ | ---- | |
| 77 | +| Leetcode Solutions | 130 | |
| 78 | +| Leetcode Kit | 100 | |
| 79 | + |
| 80 | +### **Explanation:** |
| 81 | +- **Leetcode Solutions** (ID=1) was ordered in February: |
| 82 | + \[ |
| 83 | + 60 + 70 = 130 \quad (\text{✓ included}) |
| 84 | + \] |
| 85 | +- **Jewels of Stringology** (ID=2) was ordered **only 80** times in February. (**✗ not included**) |
| 86 | +- **HP Laptop** (ID=3) was ordered **5 times** in February. (**✗ not included**) |
| 87 | +- **Lenovo Laptop** (ID=4) was **not ordered** in February. (**✗ not included**) |
| 88 | +- **Leetcode Kit** (ID=5) was ordered **100 times** in February. (**✓ included**) |
| 89 | + |
| 90 | +--- |
| 91 | + |
| 92 | +## 🖥 SQL Solution |
| 93 | + |
| 94 | +### ✅ **Using `JOIN` + `GROUP BY` + `HAVING`** |
| 95 | +#### **Explanation:** |
| 96 | +1. **Join** the `Products` and `Orders` tables on `product_id`. |
| 97 | +2. **Filter orders** placed in **February 2020** (`BETWEEN '2020-02-01' AND '2020-02-29'`). |
| 98 | +3. **Sum up the `unit` ordered** for each product. |
| 99 | +4. **Use `HAVING` to filter products with at least 100 units.** |
| 100 | +5. Return results in **any order**. |
| 101 | + |
| 102 | +```sql |
| 103 | +SELECT P.PRODUCT_NAME, SUM(O.UNIT) AS UNIT |
| 104 | +FROM PRODUCTS P |
| 105 | +INNER JOIN ORDERS O |
| 106 | +ON P.PRODUCT_ID = O.PRODUCT_ID |
| 107 | +WHERE O.ORDER_DATE BETWEEN '2020-02-01' AND '2020-02-29' |
| 108 | +GROUP BY P.PRODUCT_NAME |
| 109 | +HAVING SUM(O.UNIT) >= 100; |
| 110 | +``` |
| 111 | + |
| 112 | +--- |
| 113 | + |
| 114 | +## 🐍 Pandas Solution (Python) |
| 115 | +#### **Explanation:** |
| 116 | +1. **Merge** `products` and `orders` on `product_id`. |
| 117 | +2. **Filter only February 2020 orders**. |
| 118 | +3. **Group by `product_name`** and **sum `unit`**. |
| 119 | +4. **Filter products with at least 100 units**. |
| 120 | +5. **Return the final DataFrame**. |
| 121 | + |
| 122 | +```python |
| 123 | +import pandas as pd |
| 124 | + |
| 125 | +def products_ordered(products: pd.DataFrame, orders: pd.DataFrame) -> pd.DataFrame: |
| 126 | + # Merge both tables on product_id |
| 127 | + merged_df = pd.merge(orders, products, on="product_id", how="inner") |
| 128 | + |
| 129 | + # Convert order_date to datetime format and filter February 2020 |
| 130 | + merged_df["order_date"] = pd.to_datetime(merged_df["order_date"]) |
| 131 | + feb_orders = merged_df[ |
| 132 | + (merged_df["order_date"] >= "2020-02-01") & (merged_df["order_date"] <= "2020-02-29") |
| 133 | + ] |
| 134 | + |
| 135 | + # Group by product_name and sum the units |
| 136 | + result = feb_orders.groupby("product_name")["unit"].sum().reset_index() |
| 137 | + |
| 138 | + # Filter products with at least 100 units |
| 139 | + result = result[result["unit"] >= 100] |
| 140 | + |
| 141 | + return result |
| 142 | +``` |
| 143 | + |
| 144 | +--- |
| 145 | + |
| 146 | +## 📁 File Structure |
| 147 | +``` |
| 148 | +📂 List-Products-Ordered |
| 149 | +│── 📜 README.md |
| 150 | +│── 📜 solution.sql |
| 151 | +│── 📜 solution_pandas.py |
| 152 | +│── 📜 test_cases.sql |
| 153 | +``` |
| 154 | + |
| 155 | +--- |
| 156 | + |
| 157 | +## 🔗 Useful Links |
| 158 | +- 📖 [LeetCode Problem](https://leetcode.com/problems/list-the-products-ordered-in-a-period/) |
| 159 | +- 📚 [SQL `HAVING` Clause](https://www.w3schools.com/sql/sql_having.asp) |
| 160 | +- 🐍 [Pandas GroupBy Documentation](https://pandas.pydata.org/docs/reference/api/pandas.DataFrame.groupby.html) |
| 161 | +``` |
| 162 | +
|
| 163 | +### Features of this `README.md`: |
| 164 | +✅ **Detailed problem statement with tables** |
| 165 | +✅ **Example with step-by-step calculations** |
| 166 | +✅ **SQL and Pandas solutions with explanations** |
| 167 | +✅ **File structure for easy organization** |
| 168 | +✅ **Helpful references for further reading** |
| 169 | +
|
| 170 | +Would you like any modifications? 🚀 |
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