sql for data science with r coursera answers week 2
Practice Quiz
1. What is the function of a primary key?
- The primary key is used to identify any rows in the table that contain NULL values.
- The primary key is used to grant access to a table.
- The primary key uniquely identifies each row in a table.
- The primary key enables you to add data to columns.
2. True or False: Data Manipulation Language statements like INSERT, SELECT, UPDATE, and DELETE are used to read and modify data.
- True
- False
3. Data Definition Language (or DDL) statements are used to define, change, or delete database objects such as tables. Which of the following statements are all DDL statements?
- INSERT and UPDATE
- SELECT, INSERT, UPDATE
- SELECT and DELETE
- CREATE, ALTER, DROP
4. Which of the following queries will change the data type of an existing column (phone) to the varchar data type?
- ALTER TABLE author ALTER COLUMN phone DATA TYPE = VARCHAR(20);
- ALTER COLUMN phone SET DATA TYPE VARCHAR(20);
- ALTER TABLE author ALTER COLUMN phone SET TYPE VARCHAR(20);
- ALTER TABLE author ALTER COLUMN phone SET DATA TYPE VARCHAR(20);
5. The five basic SQL commands are:
- SELECT, COPY, PASTE, INSERT, ALTER
- CREATE, SELECT, INSERT, UPDATE, DELETE
- None of the above
- CREATE, INSERT, RETRIEVE, MODIFY, DELETE
Graded Quiz: Relational DB Concepts and Tables
6. The primary key of a relational table uniquely identifies each _______ in a table.
- row
- column
- relation
- attribute
7. Which of the following statements about a database is/are correct?
- A database is a logically coherent collection of data with some inherent meaning
- Data can only be added and queried from a database, but not modified.
- Only SQL can be used to query data in a database.
- All of the above
8. Attributes of an entity become ________ in a table.
- rows
- columns
- constraints
- keys
9. What are the basic categories of the SQL language based on functionality?
- Data Definition Language
- Data Manipulation Language
- Both of the above
- None of the above
10. The CREATE TABLE statement is a....
- DML statement
- DDL statement
- Both of the above
