SQL for Data Science Quiz Week1

Question 3
Which of the following statements are true of Entity Relationship (ER) Diagrams?

They show you the relationships between tables.

They only represent entities in the diagram.

They identify the Primary Keys

They are usually a representation of a business process.

They speed up your querying time. 

They usually are represented in a visual format. 

Key:
See the video entitled, "Data Models, Part 2: The Evolution of Data Models" for more information.

一开始全选了，但是ER  Diagrams不是只represent entities，也不能加速querying time

Question 4

The ER diagram below is depicting what kind of relationship between the EMPLOYEES and CUSTOMERS tables?

One-to-one

One-to-many  

Many-to-one

Many-to-many

Key：
See the video entitled, "Data Models, Part 3: Relational vs. Transactional Models" for more information.

一开始没看懂图，凭常识选的many-to-many，后面仔细看图，那个无限符号表示many，没有就是one

Question 8
When using the "CREATE TABLE" command and creating new columns for that table, which of the following statements is true?

You must  assign a data type to each column

You can create the table and then assign data types later 

You must insert data into all the columns while creating the table

Key：

上课这段说很快，没反复看错过了，重新看发现create table他需要给出

1. table name

2. name and definition of columns

3. data type

Question 9
Look at the values in the two columns below. Based on the values in each column, which column could potentially be used as a primary key?

 

Column 1

Column 2

Column 1 OR Column 2 
Incorrect
See the video entitled, "Creating Tables" for more information.

 Key

本来觉得1和2都可以，后面发现只能是1