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).

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

they can be modeled well, data corruption is very unlikely, and they are widely used

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. It defines how data 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

collection of data for a single item

Question 7

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

Answer 7

SQL is different! SQL is a declarative programming language. In declarative languages, programmers describe the results they want and the programming environment comes up with its own plan for getting those results.

JavaScript is imperative

Question 8

How do you retrieve specific columns from a database table?

Answer 8

select “name”

Question 9

How do you filter rows based on some specific criteria?

Answer 9

where “category” = ‘cleaning’;

Question 10

What are the benefits of formatting your SQL?

Answer 10

makes it easier to read

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 1;

at end of code

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

order by price

DESC if you want descending instead of ascending

Question 15

How do you add a row to a SQL table?

Answer 15

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

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

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

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

so it doesn’t update everything 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

delete from “products”;

Question 23

What is a foreign key?

Answer 23

The column that links two tables together since it is in both tables

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

Table aliasing like

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

Question 26

What are some examples of aggregate functions?

Answer 26

sum, avg, count

Question 27

What is the purpose of a group by clause?

Answer 27

when you want to separate rows into groups and perform aggregate functions on those groups of rows. This is done with a group by clause.