Added queries for S5 (MySQL).

Practical/Practical Exam/SQL/S5 - SQL Queries.md

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+# S5 - SQL Queries (in MySQL)
+
+**Problem Statement:**
+Consider following Relation
+Employee(emp_id,employee_name,street,city)
+Works(employee_name,company_name,salary)
+Company(company_name,city)
+Manages(employee_name,manager_name)
+Create above tables with appropriate constraints like primary key,
+foreign key, not null etc.
+1. Find the names of all employees who work for ‘TCS’.
+2. Find the names and company names of all employees sorted in
+ascending order of company name and descending order of employee
+names of that company.
+3. Change the city of employee working with InfoSys to ‘Bangalore’
+4. Find the names, street address, and cities of residence for all
+employees who work for 'TechM' and earn more than $10,000.
+5. Add Column Asset to Company table.
+
+---
+
+## Creating the database
+```sql
+CREATE DATABASE Companies;
+USE Companies;
+
+```
+
+## Creating tables:
+
+```sql
+CREATE TABLE Employee (
+  emp_id INT UNIQUE NOT NULL, -- can be set to auto increment using AUTO_INCREMENT
+  employee_name VARCHAR(255),
+  street VARCHAR(255),
+  city VARCHAR(255),
+  PRIMARY KEY (employee_name)
+);
+
+CREATE TABLE Works (
+  employee_name VARCHAR(255),
+  company_name VARCHAR(255),
+  salary INT -- use FLOAT if you are feeling fancy and pay your employees in Paise
+);
+
+CREATE TABLE Company (
+  company_name VARCHAR(255),
+  city VARCHAR(255),
+  PRIMARY KEY (company_name)
+);
+
+CREATE TABLE Manages (
+  employee_name VARCHAR(255),
+  manager_name VARCHAR(255)
+);
+
+```
+
+## Declaring foreign keys
+
+```sql
+ALTER TABLE Works ADD FOREIGN KEY (employee_name) REFERENCES Employee (employee_name);
+ALTER TABLE Works ADD FOREIGN KEY (company_name) REFERENCES Company (company_name);
+ALTER TABLE Manages ADD FOREIGN KEY (employee_name) REFERENCES Employee (employee_name);
+
+
+```
+
+## Inserting data
+
+```sql
+INSERT INTO Employee VALUES
+(1, 'Mehul', 'Street 42', 'Pune'),
+(2, 'Himanshu', 'Street 74', 'Mumbai'),
+(3, 'Gundeti', 'Street 14', 'Pune'),
+(4, 'Salvi', 'Street 38', 'Pune'),
+(5, 'Afan', 'Steet 98', 'Pune');
+
+INSERT INTO Company VALUES
+('TCS', 'Pune'),
+('Infosys', 'Mumbai'),
+('TechM', 'Pune'),
+('MEPA', 'Pune');
+
+INSERT INTO Works VALUES
+('Mehul', 'MEPA', 15000),
+('Himanshu', 'TCS', 25000),
+('Gundeti', 'TCS', 21500),
+('Salvi', 'TechM', 11000),
+('Afan', 'Infosys', 13000);
+
+
+INSERT INTO Manages VALUES
+('Mehul', 'Kalas'),
+('Himanshu', 'Kshitij'),
+('Gundeti', 'Macho'),
+('Salvi', 'Kshitij'),
+('Afan', 'Kalas');
+
+```
+
+## Queries
+
+1. Find the names of all employees who work for ‘TCS’.
+```sql
+SELECT employee_name FROM Works WHERE company_name = "TCS";
+
+```
+
+2. Find the names and company names of all employees sorted in ascending order of company name and descending order of employee names of that company.
+```sql
+SELECT company_name, employee_name FROM Works ORDER BY company_name ASC, employee_name DESC;
+
+```
+
+3. Change the city of employee working with InfoSys to ‘Bangalore’
+```sql
+UPDATE Company SET city = "Bangalore" WHERE company_name = "Infosys";
+
+```
+
+4. Find the names, street address, and cities of residence for all employees who work for 'TechM' and earn more than $10,000.
+```sql
+SELECT Employee.employee_name, Employee.street, Employee.city FROM Employee INNER JOIN Works ON Employee.employee_name = Works.employee_name WHERE Works.company_name = "TechM" AND Works.salary > 10000;
+
+```
+
+
+5. Add Column Asset to Company table.
+```sql
+ALTER TABLE Company ADD assets INT;
+
+```
+
+---