340 lines
5.5 KiB
Markdown
340 lines
5.5 KiB
Markdown
## Lecture 1 (13:00) - More SQL
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### Attribute Alias
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```sql
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SELECT driverID AS DriverNumber
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FROM Drivers;
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```
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### Distinct
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```sql
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SELECT address FROM Drivers WHERE DriverID IN (D020, D030)
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```
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#### Output:
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| address |
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|---------|
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| Dundee |
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| Dundee |
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```sql
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SELECT DISTINCT address FROM Drivers WHERE DriverID IN (D020, D030)
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```
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#### Output:
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| address |
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|---------|
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| Dundee |
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### Aggregate Functions
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- **sum()** - Adds all inputs
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- **avg()** - Mean average of all inputs
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- **count()** - Count total records of input
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- **max()** - Get maximum value of inputs
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- **min()** - Get minimum value of inputs
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### Group By
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```sql
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SELECT address, COUNT(niNo)
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FROM Employees
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GROUP BY address;
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```
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#### Output:
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| Address | count(niNo) |
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|---------|--------------|
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| Aberdeen | 2 |
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| Dundee | 2 |
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| Stirling | 1 |
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### Having Clause
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- Used with group by to filter groups / rows
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```sql
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SELECT <attributes>, <column functions>
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FROM <tables>
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WHERE <conditions> //Optional
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GROUP BY <attributes>
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HAVING <conditions>;
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```
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```sql
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SELECT address, AVG(salary)
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FROM Employees
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GROUP BY address
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HAVING AVG(salary) > 21000;
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```
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#### Output:
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| address | avg(salary) |
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|---|----|
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| Dundee | 22500 |
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### Having Vs. Where
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- **WHERE** removes rows *before* grouping
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- **HAVING** filters groups
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- Aggregate functions cannot be used with the **WHERE** clause.
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### Update Queries
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- Allows you to change the values of attributes of existing rows ( tuples ) of a table
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```sql
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UPDATE <table>
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SET <attribute assignments>
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WHERE <conditions>; //optional
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```
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```sql
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UPDATE Drivers
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SET points = 6
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WHERE driverID = "D040";
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```
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#### Output:
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```sql
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UPDATE Drivers
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SET address = "Salford"
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WHERE driverID = "D020";
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```
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### Delete Queries
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- Deletes whole rows ( tuples ), not individual values
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```sql
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DELETE FROM <table name>
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WHERE <conditions>; //optional
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```
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```sql
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DELETE FROM Drivers
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WHERE points > 10;
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```
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#### Output
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### Insert Queries
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- Adds data to existing table without deleting it or any records
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```sql
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INSERT INTO <table name> <attribute list> //optional
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SELECT <statement> | VALUES <value list>;
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```
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```sql
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INSERT INTO Drivers
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VALUES ("D060", "Betty", "Inverness", 6);
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```
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#### Output
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```sql
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INSERT INTO Drivers (driverID, name)
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VALUES ("D070", "Jeannie")
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```
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#### Output
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## Lecture 2 (15:00) - More SQL
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### Data Types
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```sql
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CHARACTER(L)
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```
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- Fixed length character string containing L letters. Fewer characters are used as padding.
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```sql
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CHARACTER VARYING(L)
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```
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- Variable length character string that holds up to L characters. No padding.
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```sql
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INTEGER(L)
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```
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- Signed whole number.
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```sql
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NUMERIC(P,S)
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```
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- P = Precision. Total number of digits
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- S = Scale. Number of digits to correct decimal place.
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- Ex. NUMERIC(5,2) is `-999.99` to `999.99`
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```sql
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DATE YYYY-MM-DD
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```
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- YYYY = `1` to `9999`
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- MM = `1` to `12`
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- DD = `1` to `31
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```sql
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TIME HH:MM:SS
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```
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- HH = Hours
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- MM = Minutes
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- SS = Seconds
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```sql
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TIMESTAMP YYYY-MM-DD HH:MM:SS
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```
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- Combination of DATE and TIME
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```sql
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INTERVAL
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```
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- Refers to period of time. May have value such as `90 days`. Also known as a span
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```sql
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BINARY LARGE OBJECT(L)
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```
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- Large, variable length binary string that can hold up to L bytes. Also known as `BLOB`
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```sql
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BOOLEAN
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```
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- Value of TRUE or FALSE
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```sql
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NULL
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```
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- Value of unknown, valid for any data type.
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#### Exercise
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1. CHAR
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2. DATE
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3. BOOLEAN
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4. INTEGER
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5. NUMERIC
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6. CHAR(10) = Bryant____
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7. VARCHAR(10) = Bryant
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8. INTEGER can have the value NULL
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### Exercise on Data Types and Keys
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1. Book
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1. ISBN - VARCHAR
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2. Title - VARCHAR
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3. Author - VARCHAR
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2. Members
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1. MemID - CHAR
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2. Name - VARCHAR
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3. Age - INTEGER
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4. Address - VARCHAR
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5. Phone - VARCHAR
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3. Loan
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1. LoanID - CHAR
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2. ISBN ( Foreign Key )
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3. MemID ( Foreign Key )
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4. LoanDate - DATE
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5. ReturnDate - DATE
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### Exercise on Adding, Deleting and Modifying Data
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1. Append tuple to pirates table
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```SQL
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INSERT INTO Pirates
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VALUES ("p5", "Pegleg", 1, 2, "Spain");
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```
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```SQL
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INSERT INTO Boats (boat-code, boat-name, origin)
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VALUES ("b9", "Swift", "British");
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```
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```SQL
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INSERT INTO Booty
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VALUES ("bt13", "Flour", 8);
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```
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1. Change the name of Booty "bt8" from "nothing" to "infected animals"
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```sql
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UPDATE Booty
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SET booty-name = "Infected Animals"
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WHERE booty-code = "bt8";
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```
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1. Remove b7 from the boats table
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```sql
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DELETE FROM Boats
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WHERE boat-code = "b7";
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```
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### Exercise on Aggregating Results
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#### Exercise
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1. Calculate total value of all booty in booty table
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```sql
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SELECT SUM(value)
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FROM booty;
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```
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1. List each type of boat, with the number of boats with that type
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```sql
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SELECT boat-type, COUNT (boat-code)
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FROM boats;
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```
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- Remember comma between select and aggregate functions
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## Workshop 1 (10:00)
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1. List the unit price of the cheapest product.
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2. What is the total value of all the products?
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3. How many products have been discontinued?
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4. What is the average unit price of the products which have been discontinued?
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5. Display the name of every supplier and the total number of products supplied by
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that company.
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6. Display total number of orders for each employee.
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