## Lecture 1 (13:00) - More SQL

### Attribute Alias

```sql
SELECT driverID AS DriverNumber
FROM Drivers;
```

### Distinct

```sql
SELECT address FROM Drivers WHERE DriverID IN (D020, D030)
```

#### Output:

| address |
|---------|
| Dundee |
| Dundee |

```sql
SELECT DISTINCT address FROM Drivers WHERE DriverID IN (D020, D030)
```

#### Output:

| address |
|---------|
| Dundee |

### Aggregate Functions

- **sum()** - Adds all inputs
- **avg()** - Mean average of all inputs
- **count()** - Count total records of input
- **max()** - Get maximum value of inputs
- **min()** - Get minimum value of inputs

### Group By

```sql 
SELECT address, COUNT(niNo)
FROM Employees
GROUP BY address;
```

#### Output:

| Address | count(niNo) |
|---------|--------------|
| Aberdeen | 2 |
| Dundee | 2 |
| Stirling | 1 |

### Having Clause

- Used with group by to filter groups / rows

```sql
SELECT <attributes>, <column functions>
FROM <tables>
WHERE <conditions> //Optional
GROUP BY <attributes>
HAVING <conditions>;
```

![](Pasted%20image%2020231003133326.png)

```sql
SELECT address, AVG(salary)
FROM Employees
GROUP BY address
HAVING AVG(salary) > 21000;
```

#### Output:

| address | avg(salary) |
|---|----|
| Dundee | 22500 |

### Having Vs. Where

- **WHERE** removes rows *before* grouping
- **HAVING** filters groups
- Aggregate functions cannot be used with the **WHERE** clause.

### Update Queries

- Allows you to change the values of attributes of existing rows ( tuples ) of a table

```sql
UPDATE <table>
SET <attribute assignments>
WHERE <conditions>; //optional
```

```sql
UPDATE Drivers
SET points = 6
WHERE driverID = "D040";
```

#### Output:

![](Pasted%20image%2020231003134123.png)

```sql
UPDATE Drivers
SET address = "Salford"
WHERE driverID = "D020";
```

![](Pasted%20image%2020231003134231.png)

### Delete Queries

- Deletes whole rows ( tuples ), not individual values

```sql
DELETE FROM <table name>
WHERE <conditions>; //optional
```

```sql
DELETE FROM Drivers
WHERE points > 10;
```

#### Output

![](Pasted%20image%2020231003134528.png)

### Insert Queries

- Adds data to existing table without deleting it or any records

```sql
INSERT INTO <table name> <attribute list> //optional
SELECT <statement> | VALUES <value list>;
```

```sql
INSERT INTO Drivers
VALUES ("D060", "Betty", "Inverness", 6);
```

#### Output

![](Pasted%20image%2020231003134918.png)

```sql
INSERT INTO Drivers (driverID, name)
VALUES ("D070", "Jeannie")
```

#### Output

![](Pasted%20image%2020231003135010.png)

## Lecture 2 (15:00) - More SQL

### Data Types

```sql
CHARACTER(L)
```

- Fixed length character string containing L letters. Fewer characters are used as padding.

```sql
CHARACTER VARYING(L)
```

- Variable length character string that holds up to L characters. No padding.

```sql
INTEGER(L)
```

- Signed whole number.

```sql
NUMERIC(P,S)
```

- P = Precision. Total number of digits
- S = Scale. Number of digits to correct decimal place.
- Ex. NUMERIC(5,2) is `-999.99` to `999.99`

```sql
DATE YYYY-MM-DD
```

- YYYY = `1` to `9999`
- MM = `1` to `12`
- DD = `1` to `31

```sql
TIME HH:MM:SS
```

- HH = Hours
- MM = Minutes
- SS = Seconds

```sql
TIMESTAMP YYYY-MM-DD HH:MM:SS
```

- Combination of DATE and TIME

```sql
INTERVAL
```

- Refers to period of time. May have value such as `90 days`. Also known as a span

```sql
BINARY LARGE OBJECT(L)
```

- Large, variable length binary string that can hold up to L bytes. Also known as `BLOB`

```sql
BOOLEAN
```

- Value of TRUE or FALSE

```sql
NULL
```

- Value of unknown, valid for any data type.

#### Exercise

1. CHAR
2. DATE
3. BOOLEAN
4. INTEGER
5. NUMERIC
6. CHAR(10) = Bryant____
7. VARCHAR(10) = Bryant
8. INTEGER can have the value NULL

### Exercise on Data Types and Keys

1. Book
	1. ISBN - VARCHAR
	2. Title - VARCHAR
	3. Author - VARCHAR
2. Members
	1. MemID - CHAR
	2. Name - VARCHAR
	3. Age - INTEGER
	4. Address - VARCHAR
	5. Phone - VARCHAR
3. Loan
	1. LoanID - CHAR
	2. ISBN ( Foreign Key )
	3. MemID ( Foreign Key )
	4. LoanDate - DATE
	5. ReturnDate - DATE

### Exercise on Adding, Deleting and Modifying Data

1. Append tuple to pirates table

```SQL
INSERT INTO Pirates
VALUES ("p5", "Pegleg", 1, 2, "Spain");
```

```SQL
INSERT INTO Boats (boat-code, boat-name, origin)
VALUES ("b9", "Swift", "British");
```

```SQL
INSERT INTO Booty
VALUES ("bt13", "Flour", 8);
```

1. Change the name of Booty "bt8" from "nothing" to "infected animals"

```sql
UPDATE Booty
SET booty-name = "Infected Animals"
WHERE booty-code = "bt8";
```

1. Remove b7 from the boats table

```sql 
DELETE FROM Boats
WHERE boat-code = "b7";
```

### Exercise on Aggregating Results

#### Exercise

1. Calculate total value of all booty in booty table

```sql 
SELECT SUM(value)
FROM booty;
```

1. List each type of boat, with the number of boats with that type

```sql
SELECT boat-type, COUNT (boat-code)
FROM boats;
```

- Remember comma between select and aggregate functions

## Workshop 1 (10:00)

![](Pasted%20image%2020231006102147.png)

1. List the unit price of the cheapest product.
![](Pasted%20image%2020231006102426.png)
2. What is the total value of all the products?
![](Pasted%20image%2020231006102826.png)
3. How many products have been discontinued?
![](Pasted%20image%2020231006102943.png)
4. What is the average unit price of the products which have been discontinued?
![](Pasted%20image%2020231006103041.png)
5. Display the name of every supplier and the total number of products supplied by
that company.
![](Pasted%20image%2020231006104220.png)
6. Display total number of orders for each employee.
![](Pasted%20image%2020231006104753.png)