PostgreSQL

Question 1

What is PostgreSQL and what are some alternative relational databases?

Answer 1

PostgreSQL is a powerful, free, open source Relational Database Management System (RDBMS). It is often cited as the most advanced open source database of its kind and is well-liked by the developer community for its robust feature set, standards compliance, and reliability.

Other popular relational databases include MySQL (also free), SQL Server by Microsoft, and Oracle by Oracle Corporation.

Question 2

What are some advantages of learning a relational database?

Answer 2

Many problem domains can be modeled well using a relational database. If you are storing related data, then a relational database is probably a good first choice!

A quality of many relational databases is that they support good guarantees about 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

sudo service postgresql status

Question 4

What is a database schema?

Answer 4

A collection of data-tables is called a schema.

A plan for your data that is has to follow.

Question 5

What is a table?

Answer 5

A table is a list of rows each having the same set of attributes.

Question 6

What is a row?

Answer 6

a single horizontal entry in the database with a set of attributes.

Question 7

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

Answer 7

Structured Query Language (SQL) is a declarative programming language to interact with relational databases. It is a powerful way of retrieving, creating, and manipulating data in a relational database.

Declarative programming language like HTML and CSS.

Question 8

How do you retrieve specific columns from a database table?

Answer 8

select

Question 9

How do you filter rows based on some specific criteria?

Answer 9

where

Question 10

What are the benefits of formatting your SQL?

Answer 10

Makes it easier to debug.

Question 11

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

Answer 11

< , >, =, and !=.

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

*

Question 14

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

Answer 14

order by

Question 15

How do you add a row to a SQL table?

Answer 15

insert

insert into “products” (“name”, “description”, “price”, “category”)
values (‘Ostrich Pillow’, ‘Feel comfy and cozy!’, 99, ‘self care’);

Question 16

What is a tuple?

Answer 16

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

Question 17

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

Answer 17

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

Question 18

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

Answer 18

returning *;

• is short for all columns.

If you only want specific values back, you can use a comma-separated list of column names instead of an * asterisk.

Question 19

How do you update rows in a database table?

Answer 19

update “products”
set “price” = 100
where “productId” = 24;

Question 20

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

Answer 20

To target specific rows to be updated.

Question 21

How do you delete rows from a database table?

Answer 21

delete from “products”
where “productId” = 24
returning *;

Question 22

How do you accidentally delete all rows from a table?

Answer 22

You don’t specify “where”.

Question 23

What is a foreign key?

Answer 23

A column that links a table to another table.

Question 24

How do you join two SQL tables?

Answer 24

select “products”.”name” as “product”,
“suppliers”.”name” as “supplier”
from “products”
join “suppliers” using (“supplierId”);

Question 25

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

Answer 25

select “products”.”name” as “product”,
“suppliers”.”name” as “supplier”
from “products”
join “suppliers” using (“supplierId”);

Question 26

What are some examples of aggregate functions?

Answer 26

max( )
Ex:
select max(“price”) as “highestPrice”
from “products”;

avg( )
Ex:
select avg(“price”) as “averagePrice”
from “products”;

count( )
Ex:
select count(*) as “totalProducts”
from “products”;

min( )
sum( )
every( )

Question 27

What is the purpose of a group by clause?

Answer 27

To separate rows into groups and perform aggregate functions on those groups of rows.

Ex:
select "category",
       avg("price") as "averagePrice"
  from "products"
 group by "category";

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( )

result.then(value => {
console.log(value);
});

Question 30

How do you handle the rejection of a Promise?

Answer 30

catch( )

result.catch(error => {
console.log(error.message);
});