Lectures

Question 1

What is a database?

Answer 1

A database is a collection of data. For example, a database could have names, addresses, birthdays, and much more.

Question 2

What is a database server AKA database management server (DBMS)?

Answer 2

The place where the database can be accessed and updated. Without this, we can’t see the data. The DBMS is persistent meaning the information never leaves.

Question 3

What is the database language?

Answer 3

It’s the language used to communicate with the database. Sometimes more than one language is used but usually just one.

Question 4

What does integrity mean to the database server?

Answer 4

It means that the information in the server can’t contradict each other. Can’t have two people with the same PK.

Question 5

What is another term for tables?

Answer 5

Relation which is why we call the table a relational model

Question 6

What is the order of the rows?

Answer 6

There is no order to the rows. It’s all just one unit.

Question 7

What is a Primary Key?

Answer 7

A PK is a unique value that identifies individual things. There can be a replication of the PK.

Question 8

What is a candidate key?

Answer 8

There can only be one PK so when there is another thing that acts as a PK it is called a candidate key.

Question 9

What is a foreign key?

Answer 9

A foreign key is a value that comes from the PK but is used in another table.

Question 10

What are the rules of a relational model?

Answer 10

• Ordering of rows doesn’t matter
• Ordering of columns doesn’t matter
• A cell has only one value
• No duplicate rows

Question 11

What is a cell with repeating values called?

Answer 11

A repeating group.

Question 12

What is a composite key?

Answer 12

When two values of a column come together to create a PK. Remember: The whole table has to depend on the Composite key, not part of it.

Question 13

How do you get rid of data redundancy?

Answer 13

By creating a composite PK.

Question 14

If there is data not dependent on the composite key.

Answer 14

The data should be removed to get rid of data redundancy. (This is the same when there’s just a PK.

Question 15

What is Null?

Answer 15

When the value is = to nothing not even itself.

Question 16

Can a PK be null?

Answer 16

No, but a foreign key can be.

Question 17

What are the rules of a foreign key?

Answer 17

They have to be part of the PK, or null.

Question 18

What is the child and parent?

Answer 18

The parent is the PK, while the child is the FK.

Question 19

What is an entity?

Answer 19

A user is interested in our data. For example, a customer.

Question 20

What is an occurrence?

Answer 20

It is the entity in the entity. For example, a single customer.

Question 21

What is the attribute?

Answer 21

Data involving the occurrence. For example, entity: customer. Occurrence: Name, address, age…

Question 22

Difference between entity/attribute type and entity/atrribute occurence?

Answer 22

The Entity would be the person using the database, while the attribute would be information to do with the entity.
The type being the main subject. Ex, entity type = person and attribute type = shovel. While the entity occurrence would be the. details of the person and the attribute occurrence would be the details of the shovel such as the price.

Question 23

How is the attribute and entity linked?

Answer 23

The entity will say what the subject is while the attribute will focus on the specifics.

Question 24

What’s is a relationship?

Answer 24

A link between PKs such as a film being assigned a classification. The word that links them is important.

Question 25

Why does a verb give classification to a relationship?

Answer 25

So that you can clarify the action with these relationships.

Question 26

What is a participation condition?

Answer 26

The rules at which something is assigned to each other, usually using the Howe/Chen notation.

Question 27

What to do when primary keys have an M-M relationship?

Answer 27

You have to add a proxy to create a different relationship. (single relationships are also better)

Question 28

Why Is having an M-M a bad thing.

Answer 28

It causes no foreign keys to be made.

Question 29

Order in which tables should be made?

Answer 29

Drop table.
Create table.
insert table.