PostgreSQL

Question 1

What is PostgreSQL and what are some alternative relational databases?

Answer 1

An open source Relational Database Management System (RDBMS); MySQL, SQL Server by Microsoft, and Oracle by Oracle Corporation.

Question 2

What are some advantages of learning a relational database?

Answer 2

Relational databases are widely used and knowing the SQL language is a portable skill that allows you to work with other databases in the future. They are also good for supporting data integrity, they can store and modify data in a way that makes data corruption as unlikely as possible.

Question 3

What is one way to see if PostgreSQL is running?

Answer 3

top command; sudo service postgresql status

Question 4

What is a database schema?

Answer 4

A collection of tables; It tells your database how data should be organized

Question 5

What is a table?

Answer 5

A list of rows with the same set of attributes

Question 6

What is a row?

Answer 6

Each entry for the table

Question 7

What is SQL and how is it different from languages like JavaScript?

Answer 7

SQL is a declarative programming language. Instead of telling the code what to do, you describe the results you want.

Question 8

How do you retrieve specific columns from a database table?

Answer 8

select “column”

Question 9

How do you filter rows based on some specific criteria?

Answer 9

where clause

Question 10

What are the benefits of formatting your SQL?

Answer 10

Readability

Question 11

What are four comparison operators that can be used in a where clause?

Answer 11

=, >, =, <=, <> (not equal)

Question 12

How do you limit the number of rows returned in a result set?

Answer 12

limit clause

Question 13

How do you retrieve all columns from a database table?

Answer 13

asterisk

Question 14

How do you control the sort order of a result set?

Answer 14

order by “column”; desc if you want it in descending order

Question 15

How do you add a row to a SQL table?

Answer 15

insert statement

Question 16

What is a tuple?

Answer 16

a list of values

Question 17

How do you add multiple rows to a SQL table at once?

Answer 17

use a comma after each entry for values

Question 18

How do you get back the row being inserted into a table without a separate select statement?

Answer 18

returning clause

Question 19

How do you update rows in a database table?

Answer 19

update statement

Question 20

Why is it important to include a where clause in your update statements?

Answer 20

If you don’t, it will update everything in the table

Question 21

How do you delete rows from a database table?

Answer 21

delete statement and where clause

Question 22

How do you accidentally delete all rows from a table?

Answer 22

Not specifying a where clause

Question 23

What is a foreign key?

Answer 23

a key used to link two tables together

Question 24

How do you join two SQL tables?

Answer 24

join clause “table” using clause (‘column’)

Question 25

How do you temporarily rename columns or tables in a SQL statement?

Answer 25

as clause

Question 26

What are some examples of aggregate functions?

Answer 26

count(), sum(), avg()

Question 27

What is the purpose of a group by clause?

Answer 27

to select specific rows to perform aggregate functions on

Question 28

What are the three states a Promise can be in?

Answer 28

pending, fulfilled, rejected

Question 29

How do you handle the fulfillment of a Promise?

Answer 29

then() method

Question 30

How do you handle the rejection of a Promise?

Answer 30

catch() method