postgres/sql

Question 1

Why do we use databases in Web development?

Answer 1

to store data and information

Question 2

What is PostgreSQL and what are some alternative relational databases?

Answer 2

PostgreSQL is a data management system and other alternatives include Oracle, MySQL

Question 3

What are some advantages of learning a relational database?

Answer 3

Ease of use, open source, flexibility

Question 4

What is one way to see if PostgreSQL is running?

Answer 4

sudo service postgresql status

Question 5

What is a database schema?

Answer 5

it shows how a data is organized within the database

Question 6

What is a table?

Answer 6

rows and columns used to store data titles and the data itself

Question 7

What is a row?

Answer 7

the horizontal part of the table

Question 8

What is an attribute and what other names are used to describe them?

Answer 8

an attribute in postgresql is the column in the postgresql table it shows the information of the data type

Question 9

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

Answer 9

Structured query language (SQL) is a way to interact with databases and it is different from JavaScript you tell it how to do it while in SQL you ask what you want

Question 10

How do you retrieve specific columns from a database table?

Answer 10

by using the select clause
(ex. select “firstName”, “lastName”
from “table_name”)

Question 11

How do you filter rows based on some specific criteria?

Answer 11

by using the where clause
(ex. where “lastName” = ‘Lee’)

Question 12

What are the benefits of formatting your SQL?

Answer 12

for readability purposes

Question 13

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

Answer 13

= < > <= >= !=

Question 14

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

Answer 14

by using the limit clause
(ex. limit 10;)

Question 15

How do you retrieve all columns from a database table?

Answer 15

by using an *
(ex. select *
from “table_name”;)

Question 16

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

Answer 16

by using the order by clause
(ex. order of “price”;)

Question 17

How do you add a row to a SQL table?

Answer 17

by using the insert into keyword
(ex. insert into “students” (“name”, “age”))

Question 18

What is a tuple?

Answer 18

the list of values

Question 19

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

Answer 19

by adding multiple tuples

Question 20

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

Answer 20

by using the returning keyword
(ex. returning *;)

Question 21

How do you update rows in a database table?

Answer 21

by using the update keyword
(ex. update “student”
set “name” = “Timothy Lee”
where “studentId” = 2;)

Question 22

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

Answer 22

So it knows which row to update

Question 23

How do you delete rows from a database table?

Answer 23

by using the delete keyword
(ex. delete from “student”
where “studentId” = 2;)

Question 24

How do you accidentally delete all rows from a table?

Answer 24

by not putting where to delete
(ex. delete from “student”;)

Question 25

What is a foreign key?

Answer 25

it is a primary key from a different table

Question 26

How do you join two SQL tables?

Answer 26

by using the join keyword
(ex. select “p”.”amount”, “c”.”firstName”,
from “payment” as “p”
join “customers” as “c” using (“customerId”)
)

Question 27

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

Answer 27

by using the as keyword
(ex. select g.name as genre
from genres as g)

Question 28

What are some examples of aggregate functions?

Answer 28

sum(), avg(), count(), min(), max(), total()

Question 29

What is the purpose of a group by clause?

Answer 29

so that the aggregate function is applied to only that group

Question 30

What are JavaScript classes?

Answer 30

classes are used to create objects that have properties and methods, they also provide a more structured way to define and create objects

Question 31

When would you want to use a class?

Question 32

How do you declare a class?

Answer 32

by using the class keyword
(ex.
class Shape {
constructor (area, circumference)
}
)

Question 33

How do you inherit from another class?

Answer 33

by using the extends keyword
(ex.
class Square extends Shape {
}
)

Question 34

Why would you want to inherit from another class?

Answer 34

so that you can reuse the code instead of writing it all over again

Question 35

How do you add methods and properties to a class?

Answer 35

by adding it within the class object using functions