SQL

Question 1

What is PostgreSQL and what are some alternative relational databases?

Answer 1

it’s an open source relational database, alts are mySQL, SQLite, SnowFlake

Question 2

What are some advantages of learning a relational database?

Answer 2

they’re everywhere so if you learn one, you learn a lot of them

Question 3

What is one way to see if PostgreSQL is running?

Answer 3

check top or sudo service postgresql status

Question 4

What is a database schema?

Answer 4

a collection of tables in a database

Question 5

What is a table?

Answer 5

a list of rows all having the same attributes

Question 6

What is a row?

Answer 6

one entry in a table that has an attribute value

Question 7

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

Answer 7

its a declarative language vs JS is imperative

Question 8

How do you retrieve specific columns from a database table?

Answer 8

select “column name”
“additional columns. . .”
from “table name”;

Question 9

How do you filter rows based on some specific criteria?

Answer 9

where clause and an expression that evaluates to a boolean

Question 10

What are the benefits of formatting your SQL?

Answer 10

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 clause

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 clause with asc and desc

Question 15

How do you add a row to a SQL table?

Answer 15

insert into statement

Question 16

What is a tuple?

Answer 16

a list of values that may or may not correspond to a row in a table

Question 17

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

Answer 17

insert into with one list of columns followed with multiple tuples

Question 18

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

Answer 18

returning *

Question 19

How do you update rows in a database table?

Answer 19

update keyword(update “tableName” set “column” = ‘value’)

Question 20

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

Answer 20

if you don’t it will update every row

Question 21

How do you delete rows from a database table?

Answer 21

delete keyword (delete from “table” where “something” = something else)

Question 22

How do you accidentally delete all rows from a table?

Answer 22

by not including a where clause

Question 23

What is a foreign key?

Answer 23

rows between tables with shared values

Question 24

How do you join two SQL tables?

Answer 24

join “table” using (“key”)

Question 25

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

Answer 25

using an alias with keyword “as”

Question 26

What are some examples of aggregate functions?

Answer 26

sum(), avg(), count(), min(), max(), every()

Question 27

What is the purpose of a group by clause?