PostgreSQL

Question 1

What is PostgreSQL and what are some alternative relational databases?

Answer 1

It is a relational database that is popular.

Question 2

What are some advantages of learning a relational database?

Answer 2

You can learn other relational database just as fast due to similarities

Question 3

What is one way to see if PostgreSQL is running?

Answer 3

sudo service postgresql status

Question 4

What is a database schema?

Answer 4

Collection of tables

Question 5

What is a table?

Answer 5

tables are relations

Question 6

What is a row?

Answer 6

data about columns

Question 7

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

Answer 7

Structured Query Language and declarative programming language much like HTML and CSS
(You tell it what to do)

Question 8

How do you retrieve specific columns from a database table?

Answer 8

Use select “columnName”

Question 9

How do you filter rows based on some specific criteria?

Answer 9

Use where “columnName” operator (=, >, < e.t.c) ‘value’

Question 10

What are the benefits of formatting your SQL?

Answer 10

Better readability and looks clean

Question 11

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

Answer 11

equal, not equal, greater than, less than (equal to)

Question 12

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

Answer 12

Use limit value

Question 13

How do you retrieve all columns from a database table?

Answer 13

Use select asterisk (*)

Question 14

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

Answer 14

Use order by “columnName” desc (by default it is ascending)

Question 15

How do you add a row to a SQL table?

Answer 15

insert into “tableName” (“columnName”, …)

values (‘value’, …)

Question 16

What is a tuple?

Answer 16

List of values

Question 17

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

Answer 17

add more values (‘value’, …)

separated by comma (much like select)

Question 18

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

Answer 18

add returning * at the end

Question 19

How do you delete rows from a database table?

Answer 19

delete from “tableName”
where “columnName” operator ‘value’
and “columnName” operator ‘value’
(Use and for when multiple things should be true)

Question 20

How do you accidentally delete all rows from a table?

Answer 20

when you simply do

delete from “tableName”

Question 21

What is a foreign key?

Answer 21

Basically a mutual column from two different tables

Question 22

How do you join two SQL tables?

Answer 22

join “tableName” using (“columnName”)

Question 23

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

Answer 23

Use alias using (as) then aliasName

Question 24

What are some examples of aggregate functions?

Answer 24

min(), max(), count(), avg()

Question 25

What is the purpose of a group by clause?

Answer 25

it literally groups them nicely