DatabaseManagementSystems/Practical/Practical Exam/SQL/S7 - SQL Queries.md

# S7 - 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. Change the city of employee working with InfoSys to ‘Bangalore’
2. Find the names of all employees who earn more than the average
salary of all employees of their company. Assume that all people
work for at most one company.
3. Find the names, street address, and cities of residence for all
employees who work for 'TechM' and earn more than $10,000.
4. Change name of table Manages to Management.
5. Create Simple and Unique index on employee table.
6. Display index Information

---

## Creating the database
```sql
CREATE DATABASE Bank4;
USE Bank4;

```

## Creating tables:

```sql
CREATE TABLE Account (
  acc_no INT,
  branch_name VARCHAR(255),
  balance INT,
  PRIMARY KEY (acc_no)
);

CREATE TABLE Branch (
  branch_name VARCHAR(255),
  branch_city VARCHAR(255),
  assets INT,
  PRIMARY KEY (branch_name)
);

CREATE TABLE Customer (
  cust_name VARCHAR(255),
  cust_street VARCHAR(255),
  cust_city VARCHAR(255),
  PRIMARY KEY (cust_name)
);

CREATE TABLE Depositor (
  cust_name VARCHAR(255),
  acc_no INT
);

CREATE TABLE Loan (
  loan_no INT,
  branch_name VARCHAR(255),
  amount INT,
  PRIMARY KEY (loan_no)
);

CREATE TABLE Borrower (
  cust_name VARCHAR(255),
  loan_no INT
);

```

## Declaring foreign keys

```sql
ALTER TABLE Account ADD FOREIGN KEY (branch_name) REFERENCES Branch (branch_name);
ALTER TABLE Depositor ADD FOREIGN KEY (cust_name) REFERENCES Customer (cust_name);
ALTER TABLE Depositor ADD FOREIGN KEY (acc_no) REFERENCES Account (acc_no);
ALTER TABLE Loan ADD FOREIGN KEY (branch_name) REFERENCES Branch (branch_name);
ALTER TABLE Borrower ADD FOREIGN KEY (cust_name) REFERENCES Customer (cust_name);
ALTER TABLE Borrower ADD FOREIGN KEY (loan_no) REFERENCES Loan (loan_no);

```

## Inserting data

```sql
INSERT INTO Branch VALUES
('Pune_Station', 'Pune', 50000),
('PES', 'Pune', 65000),
('Lohegaon', 'Pune', 350000),
('Viman Nagar', 'Pune', 850000);

INSERT INTO Customer VALUES
('Kalas', 'Street 12', 'Pune'),
('Himanshu', 'Street 15', 'Pune'),
('Mehul', 'Street 29', 'Pune'),
('Macho', 'Street 59', 'Mumbai'),
('Gundeti', 'Street 40', 'Mumbai'),
('Salvi', 'Street 8', 'Pune'),
('Pintu', 'Street 55', 'Ahemadnagar'),
('Piyush', 'Street 21', 'Assam');

INSERT INTO Account VALUES
(101, 'Lohegaon', 67000),
(102, 'PES', 4324),
(103, 'PES', 54670),
(104, 'Viman Nagar', 5433),
(105, 'Pune_Station', 6462);

INSERT INTO Depositor VALUES
('Kalas', 101),
('Macho', 104),
('Gundeti', 105),
('Salvi', 105);

INSERT INTO Loan VALUES
(201, 'Pune_Station', 1800),
(202, 'PES', 8500),
(203, 'PES', 15000),
(204, 'Pune_Station', 5322),
(205, 'Viman Nagar', 1300),
(206, 'Lohegaon', 1450);

INSERT INTO Borrower VALUES
('Macho', 201),
('Mehul', 202),
('Himanshu', 203),
('Salvi', 204);

```

## Queries

1. Create a View1 to display List all customers in alphabetical order who have loan from Pune_Station branch.
```sql
CREATE VIEW View1 AS SELECT cust_name FROM Borrower INNER JOIN Loan ON Borrower.loan_no = Loan.loan_no WHERE branch_name = "Pune_Station" ORDER BY cust_name;
SELECT * FROM View1;

```

2. Create View2 on branch table by selecting any two columns and perform insert update delete operations.
```sql
-- Creating view
CREATE VIEW View2 AS SELECT branch_name, assets FROM Branch;
SELECT * FROM View2;

-- Insert operation
INSERT INTO View2 VALUES ('Kharadi', 594000);
INSERT INTO View2 VALUES ('Yerwada', 34004);
SELECT * FROM View2;

-- Update operation
UPDATE View2 SET assets = 590000 WHERE branch_name = "Kharadi";
UPDATE View2 SET assets = 24000 WHERE branch_name = "Yerwada";
SELECT * FROM View2;

-- Delete
DELETE FROM View2 WHERE branch_name = "Yerwada";
SELECT * FROM View2;

```

3. Create View3 on borrower and depositor table by selecting any one column from each table perform insert update delete operations.
```sql
-- Creating view
CREATE VIEW View3 AS SELECT Borrower.cust_name, Depositor.acc_no FROM Borrower JOIN Depositor ON Borrower.cust_name = Depositor.cust_name;
SELECT * FROM View3;

-- Insert operation
INSERT INTO Borrower (cust_name, loan_no) VALUES ('Pintu', 205);
INSERT INTO Depositor (cust_name, acc_no) VALUES ('Pintu', 102);
SELECT * FROM View3;

-- Update operation
UPDATE View3 SET cust_name = "Piyush" WHERE cust_name = "Pintu";
SELECT * FROM View3;

-- Delete operation
DELETE FROM Borrower WHERE cust_name = 'Macho';
-- This will also remove it from View3. We cannot perform delete operation directly View3 since it is created using join clause
SELECT * FROM View3;

```

4. Create Union of left and right joint for all customers who have an account or loan or both at bank
```sql
SELECT Borrower.cust_name FROM Borrower LEFT JOIN Loan ON Borrower.loan_no = Loan.loan_no UNION SELECT Depositor.cust_name FROM Depositor RIGHT JOIN Account ON Depositor.acc_no = Account.acc_no;

```

5. Create Simple and Unique index.
```sql
-- Simple Index
CREATE INDEX loaners ON Borrower(cust_name);

-- Unique Index
CREATE UNIQUE INDEX depos ON Depositor(cust_name);

```

6. Display index Information.
```sql
SHOW INDEX FROM Borrower;
SHOW INDEX FROM Depositor;

```

---