Sequel/Databases

Question 1

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

Answer 1

coding language used to interact with databases

Question 2

How do you retrieve specific columns from a database table?

Answer 2

select

Question 3

How do you filter rows based on some specific criteria?

Answer 3

where “column” = ‘condition’

Question 4

What are the benefits of formatting your SQL?

Answer 4

more easily readable

Question 5

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

Answer 5

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

Question 6

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

Answer 6

limit (number);

Question 7

How do you retrieve all columns from a database table?

Answer 7

select *

Question 8

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

Answer 8

desc keyword after the statement

order by “price” desc

Question 9

How do you add a row to a SQL table?

Answer 9

insert into “table” (values)

Question 10

What is a tuple?

Answer 10

In SQL, a list of values is referred to as a tuple.

Question 11

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

Answer 11

Data rows can be batch inserted into a database table by specifying more than one tuple of values, separated by commas.

Question 12

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

Answer 12

returning *;

Question 13

How do you update rows in a database table?

Answer 13

update statement

Question 14

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

Answer 14

sets a limit to prevent all values from being changed

Question 15

How do you delete rows from a database table?

Answer 15

delete statement

Question 16

How do you accidentally delete all rows from a table?

Answer 16

dont include a where statement

Question 17

What is a foreign key?

Answer 17

a value in a column that can be used to link two tables

Question 18

How do you join two SQL tables?

Answer 18

select “firstName”,
“lastName”
from “customers”
join “payments” using (“customerId”)

Question 19

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

Answer 19

aliases

Question 20

What are some examples of aggregate functions?

Answer 20

Aggregate functions compute a single result from a set of input values. sum() avg()

Question 21

What is the purpose of a group by clause?

Answer 21

to separate rows into groups and perform aggregate functions on those groups of rows

Question 22

What are the three states a Promise can be in?

Answer 22

pending, rejected, fulfilled

Question 23

How do you handle the fulfillment of a Promise?

Answer 23

.then

Question 24

How do you handle the rejection of a Promise?

Answer 24

.catch

Question 25

What does fetch() return?

Answer 25

returns a promise containing the response (a Response object).

Question 26

What is the default request method used by fetch()?

Answer 26

get

Question 27

How do you specify the request method (GET, POST, etc.) when calling fetch?

Answer 27

with the 2nd parameter (init)
fetch(‘link’, {
method: ‘POST’
}

Question 28

When does React call a component’s componentDidMount method?

Answer 28

after the first successful render

Question 29

Name three React.Component lifecycle methods.

Answer 29

constructor render componentdidmount

Question 30

How do you pass data to a child component?

Answer 30

props

Question 31

What does express.static() return?

Answer 31

a middleware function

Question 32

What is the local __dirname variable in a Node.js module?

Answer 32

The directory name of the current module. This is the same as the path.dirname() of the __filename.

It starts with / so it is absolute file path since it starts at the root of the file system

Question 33

What does the join() method of Node’s path module do?

Answer 33

The path.join() method joins all given path segments together using the platform-specific separator as a delimiter, then normalizes the resulting path.