## Lecture 1 (13:00) - Conceptual Modelling

### Role of Conceptual Modelling

- Real world problem -> Conceptual Model Data -> Logical Data Model -> Physical Model (DBMS)
	- Identify important concepts and data needs, creating a conceptual model.
- Many different ways to get to the same solution.
- Iterative process - if one method does not work, it can be revised.

### Conceptual Data Model

- Abstract view of situation.
	- Identifies important elements and relationships between them. (ex. Library: Books, Members, ~~Carpets~~)
	- Human interact-able, not computer terms.
	- Implementation Independent.
	- Useful for client brief.

### Reasons for Using ER Modelling

- Simpler and easier to understand than database tables
	- Helps discussions with clients and colleagues
- Allows for segmentation of work.
	- Modelling real world solution
	- Designing DB tables
- Most large organisations will require it

### Obtaining an ER Model

- Given a spec, you need to identify:
	- entities - 'things' with physical or conceptual existence
	- relationships
	- attributes
	- constraints or assumptions

#### Example

Departments control many projects and each department has many employees. Each employee works on only one project at a time. A project’s start date must be before the project’s target completion date. Each employee has an NI number, name and address

Entities:

- departments
- projects
- employees
Relationships:
- **control** between departments and projects
- **has between** departments and employees
- **works on** between employees and projects
Attributes:
- startdate
- completiondate
- ninumber
- name
- address
Constraints:
- Start date must be before the target completion date

### ER Diagram

![](Pasted%20image%2020231017132317.png)

- Many different notations
- One is "crows foot":
![](Pasted%20image%2020231017132357.png)
![](Pasted%20image%2020231017133438.png)
![](Pasted%20image%2020231017133451.png)

## Lecture 3 (16:00)

1. Generate a list of the ages of ATMs whose security level is normal. The list should be in descending order.

```sql
SELECT age
FROM atm
WHERE security-level = "normal"
ORDER BY age DESC;
```

1. List the name of each bank which has a branch whose address starts with the word Eccles. The list should not include any duplicates.

```sql
SELECT DISTINCT name
FROM bank, branch
WHERE Bank.bankID = Branch.bankID 
AND address LIKE "Eccles*";
```

1. Calculate the average age of the ATMs with low or normal levels of security. Name the results column “Average age”.

```sql
SELECT AVG(age) AS "Average Age"
FROM atm
WHERE security-level = "low" OR security-level = "normal";
```

1. Remove the tuple from the relation ATM whose identifier is atm04.

```sql
DELETE FROM atm
WHERE atmID = "atm04";
```

1. Add a row for an ATM, whose atmID is atm05, whose security level is high and which is located at branch T1.

```sql
INSERT INTO atm 
VALUES ("atm05", "high", "0", "T1");
```

1. Add an attribute called telephone number to the relation Branch.

```sql
ALTER TABLE branch
ADD telephone CHAR(15)
```

1. Set the address of every branch to the value Salford.

```sql
UPDATE branch
SET address = "Salford";
```

1. Bank LEFT OUTER JOIN Branch

```sql
SELECT *
FROM bank
INNER JOIN 
```