PostgreSQL

Question 1

What is PostgreSQL and what are some alternative relational databases?

Answer 1

Relational database system.

SQLite, MySQL, Oracle, SQL Azure, Teradata

Question 2

What are some advantages of learning a relational database?

Answer 2

Relational databases are commonly referred to as “SQL databases” because you usually do work with them using some variation of the SQL language.

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 tables is called a schema. A schema defines how the data in a relational database should be organized.

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

You might visualize a database table as a sort of spreadsheet where each row is a record in that spreadsheet.

Question 7

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

Answer 7

You may be familiar with imperative programming languages such as JavaScript, where you basically tell the JavaScript runtime what to do and how to do it.

QL is a declarative programming language. In declarative languages, programmers describe the results they want.

Question 8

How do you retrieve specific columns from a database table?

Answer 8

select “column name”
from “table”

Question 9

How do you filter rows based on some specific criteria?

Answer 9

where “filter topic” = ‘category’

Question 10

What are the benefits of formatting your SQL?

Answer 10

SQL does not have to be indented, but you should do it anyway for consistent style and therefore readability.

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 *

Question 14

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

Answer 14

desc
(The default sort order of the results is ascending order)

Question 15

How do you add a row to a SQL table?

Answer 15

insert into “table” (‘column name’)
values (‘value’)

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

insert into “products” (“name”, “description”, “price”, “category”)

values (‘Ostrich Pillow’, ‘Feel comfy and cozy!’, 99, ‘self care’),
(‘Tater Mitts’, ‘Scrub some taters!’, 6, ‘cooking’)
returning *;

Question 18

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

Answer 18

returning *;

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;

Question 20

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

Answer 20

it would update every row in the table!

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

if you don’t specify “where”

Question 23

What is a foreign key?

Answer 23

usually IDs

Question 24

How do you join two SQL tables?

Answer 24

select *
from “products”
join “suppliers” using (“supplierId”);

Question 25

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

Answer 25

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