PostgreSQL/SQL

Question 1

What is PostgreSQL and what are some alternative relational databases?

Answer 1

Open source relational database server

Other databases: SQLite, SQL Server, Oracle SQL

Question 2

What are some advantages of learning a relational database?

Answer 2

Great if you are storing related data. Less likelihood of data corruption. Most importantly: you will use it as a developer.

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

Dictates how data should be organized

Question 5

What is a table?

Answer 5

Organized rows that have the same set of attributes. Overall, a place where data can be stored

Question 6

What is a row?

Answer 6

One record in a table

Question 7

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

Answer 7

Its a declarative language meaning you tell what you want and the language will interpret it. On the other hand, JS is imperative meaning you have to tell it exactly what you want it to do.

Question 8

How do you retrieve specific columns from a database table?

Answer 8

select “column”

from “table”;

Question 9

How do you filter rows based on some specific criteria?

Answer 9

where clause “column” = ‘data’

Question 10

What are the benefits of formatting your SQL?

Answer 10

SQL can get very complex. Structuring it will make it easier to read.

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 clause

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 “column” desc/asc

Question 15

How do you add a row to a SQL table?

Answer 15

insert into “table” (“column”, “column”)

Question 16

What is a tuple?

Answer 16

Specific ordered list with paranthesis

Question 17

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

Answer 17

values (‘data’, ‘data’) separated by comma

Question 18

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

Answer 18

returning clause

Question 19

How do you update rows in a database table?

Answer 19

update “table”
set “column” = ‘data’
where “column” = ‘data’

Question 20

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

Answer 20

So you don’t update all the rows

Question 21

How do you delete rows from a database table?

Answer 21

delete from “table”

where “column” = ‘data’

Question 22

How do you accidentally delete all rows from a table?

Answer 22

delete from “table” with no other clauses

Question 23

What is a foreign key?

Answer 23

Columns that refer to another column in a different table. Data should match.

Question 24

How do you join two SQL tables?

Answer 24

join “table” using (“column”)

Question 25

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

Answer 25

as keyword which also refers to alias

Question 26

What are some examples of aggregate functions?

Answer 26

average, max, min, sum, amount

Question 27

What is the purpose of a group by clause?

Answer 27

Separate rows by groups