SQL Exercises

MYSQL/1757_RecyclableAndLowFatProducts.md

@@ -0,0 +1,73 @@
+# 1757. Recyclable and Low Fat Products
+* **Topic** --> **_SQL Schema_** 
+* Has been asked in **Facebook** interviews **4** times. 
+---
+## Task Introduction 
+* **_product_id_** is the primary key for this table. low_fats is an ENUM of type ('Y', 'N') where 'Y' means this product is low fat and 'N' means it is not. **_recyclable_** is an ENUM of types ('Y', 'N') where 'Y' means this product is recyclable and 'N' means it is not. 
+
+```sh
+Table Name: Products 
++-------------+---------+
+| Column Name | Type    |
++-------------+---------+
+| product_id  | int     |
+| low_fats    | enum    |
+| recyclable  | enum    |
++-------------+---------+
+```
+
+#### **_To Do 1_**: Write an SQL query to find the ids of products that are both low fat and recyclable.
+#### **_To Do 2_**: Return the result table in **any order**.
+#### **_To Do 3_**: The query result format is in the following example.
+
+##### **Example 1**
+```sh
+Input: 
+Products table:
++-------------+----------+------------+
+| product_id  | low_fats | recyclable |
++-------------+----------+------------+
+| 0           | Y        | N          |
+| 1           | Y        | Y          |
+| 2           | N        | Y          |
+| 3           | Y        | Y          |
+| 4           | N        | N          |
++-------------+----------+------------+
+Output: 
++-------------+
+| product_id  |
++-------------+
+| 1           |
+| 3           |
++-------------+
+Explanation: Only products 1 and 3 are both low fat and recyclable.
+```
+---
+## Solution
+```SQL
+SELECT product_id -- to find the ids of products that are both low fat and recyclable
+FROM Products 
+WHERE low_fats = 'Y'
+AND recyclable = 'Y'
+```
+
+```sh 
+Input: Products =
++------------+----------+------------+
+| product_id | low_fats | recyclable |
+| ---------- | -------- | ---------- |
+| 0          | Y        | N          |
+| 1          | Y        | Y          |
+| 2          | N        | Y          |
+| 3          | Y        | Y          |
+| 4          | N        | N          |
++------------+----------+------------+
+
+Expected: 
++------------+
+| product_id |
+| ---------- |
+| 1          |
+| 3          |
++------------+
+```

MYSQL/1757_RecyclableandLowFatProducts.sql

@@ -0,0 +1,4 @@
+SELECT product_id -- to find the ids of products that are both low fat and recyclable
+FROM Products 
+WHERE low_fats = 'Y'
+AND recyclable = 'Y'

MYSQL/584_FindCustomerReferee.md

@@ -0,0 +1,38 @@
+# 584 Find Customer Referee
+* **Topic** --> **_SQL Schema_** 
+
+---
+## Task Introduction 
+* Find the names of the customer that **are not referred** by the customer with **id = 2**. Return the result table in **any order**.The result format is in the following example.
+
+```sh
+Input: Customer table:
++----+------+------------+
+| id | name | referee_id |
++----+------+------------+
+| 1  | Will | null       |
+| 2  | Jane | null       |
+| 3  | Alex | 2          |
+| 4  | Bill | null       |
+| 5  | Zack | 1          |
+| 6  | Mark | 2          |
++----+------+------------+
+Output: 
++------+
+| name |
++------+
+| Will |
+| Jane |
+| Bill |
+| Zack |
++------+
+```
+
+---
+## Solution
+```SQL
+SELECT name
+FROM Customer
+WHERE referee_id <> 2
+OR referee_id IS NULL
+```

MYSQL/584_FindCustomerReferee.sql

@@ -0,0 +1,5 @@
+SELECT name
+FROM Customer
+WHERE referee_id <> 2
+OR referee_id IS NULL
+

MYSQL/595_BigCountries.md

@@ -0,0 +1,68 @@
+# 595.Big Countries
+* **Topic** --> **_SQL Schema_** 
+---
+## Task Introduction 
+* Name is the primary ey column for the below table. Each row of this table gives information about the name of a country, the continent to which it blongs, its area, the population, and its GDP value. 
+
+```sh
+Table Name: World 
++-------------+---------+
+| Column Name | Type    |
++-------------+---------+
+| name        | varchar |
+| continent   | varchar |
+| area        | int     |
+| population  | int     |
+| gdp         | bigint  |
++-------------+---------+
+```
+
+* A country is **_big_** if:
+  * it has an area of at least three million (i.e 300000 km^2), or
+  * it has a population of at least twenty-five million (i.e. 25000000).
+#### **_To Do 1_**: Write an SQL query to report the name, population, and area of the **big countries**.
+#### **_To Do 2_**: Return the result table in **any order**.
+#### **_To Do 3_**: Return the result table in **any order**.
+##### **Example 1**
+```sh
+Input: 
+World table:
++-------------+-----------+---------+------------+--------------+
+| name        | continent | area    | population | gdp          |
++-------------+-----------+---------+------------+--------------+
+| Afghanistan | Asia      | 652230  | 25500100   | 20343000000  |
+| Albania     | Europe    | 28748   | 2831741    | 12960000000  |
+| Algeria     | Africa    | 2381741 | 37100000   | 188681000000 |
+| Andorra     | Europe    | 468     | 78115      | 3712000000   |
+| Angola      | Africa    | 1246700 | 20609294   | 100990000000 |
++-------------+-----------+---------+------------+--------------+
+Output: 
++-------------+------------+---------+
+| name        | population | area    |
++-------------+------------+---------+
+| Afghanistan | 25500100   | 652230  |
+| Algeria     | 37100000   | 2381741 |
++-------------+------------+---------+
+```
+--- 
+## Solution
+```SQL
+SELECT name, population,area
+FROM World 
+WHERE area >= 3000000
+OR population >= 25000000
+```
+
+```sh
+Output: 
+| name        | population | area    |
+| ----------- | ---------- | ------- |
+| Afghanistan | 25500100   | 652230  |
+| Algeria     | 37100000   | 2381741 |
+
+Expected: 
+| name        | population | area    |
+| ----------- | ---------- | ------- |
+| Afghanistan | 25500100   | 652230  |
+| Algeria     | 37100000   | 2381741 |
+```

MYSQL/595_BigCountries.sql

@@ -0,0 +1,4 @@
+SELECT name, population,area
+FROM World 
+WHERE area >= 3000000
+OR population >= 25000000