PostgreSQL

Question 1

What is PostgreSQL and what are some alternative relational databases?

Answer 1

a relational database management system (RDBMS), MySQL, SQLite, SQL microsoft, Oracle

Question 2

What are some advantages of learning a relational database?

Answer 2

easy to reject “bad” data (half written). Easy to store and modify data in a way that makes data corruption as unlikely as possible, widely use

Question 3

What is one way to see if PostgreSQL is running?

Answer 3

sudo service postgresql status, TOP command in terminal.

Question 4

What is a database schema?

Answer 4

collection of tables, defines how the data in a relational database should be organized.

Question 5

What is a table?

Answer 5

A list of rows each having the same set of attributes

Question 6

What is a row?

Answer 6

data to fill each attributes

Question 7

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

Answer 7

SQL is a declarative programming language -> programmers describe the results they want and the programming environment comes up with its own plan for getting those results.
JavaScript is an imperative programming language -> you tell programming environment what to do and how to do it.

Question 8

How do you retrieve specific columns from a database table?

Answer 8

select “column1”, “column2”, … from

Question 9

How do you filter rows based on some specific criteria?

Answer 9

where “column” = ‘something’

Question 10

What are the benefits of formatting your SQL?

Answer 10

easier to read top to bottom than left to right

Question 11

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

Answer 11

=, <, >, !=

Question 12

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

Answer 12

limit ##

Question 13

How do you retrieve all columns from a database table?

Answer 13

select * from database_table

Question 14

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

Answer 14

sort by desc

Question 15

How do you add a row to a SQL table?

Answer 15

insert into “database_name” (“columnName”, …)
value (‘value1’, …), (‘value##’, …), …

Question 16

What is a tuple?

Answer 16

list of value, has order.

Question 17

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

Answer 17

value (‘value1’, …), (‘value##’, …), …

Question 18

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

Answer 18

insert into ….
value ….
returning *;

Question 19

How do you update rows in a database table?

Answer 19

update “table_name”
set “column_name” = ‘new value’
where “column_name” = ‘old value’;

Question 20

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

Answer 20

otherwise it update ALL the rows.

Question 21

How do you delete rows from a database table?

Answer 21

delete
from “table_name”
where “column_name” = ‘value’
[and ….];

Question 22

How do you accidentally delete all rows from a table?

Answer 22

delete
from “table_name”;

Question 23

What is a foreign key?

Answer 23

common value[s] (of column) between tables

Question 24

How do you join two SQL tables?

Answer 24

select “columnName”
from “table1”
join “table2” using (“foreign key”)
[where …. , limit …, order by ….]

Question 25

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

Answer 25

“table_name”.”columnName” as “newName”

Question 26

What are some examples of aggregate functions?

Answer 26

sum(), count(), average()

Question 27

What is the purpose of a group by clause?

Answer 27

group result set into bucket by row(s)

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

myPromise.then(value)

Question 30

How do you handle the rejection of a Promise?

Answer 30

myPromise.catch(err)