SQL

Question 1

What is PostgreSQL and what are some alternative relational databases?

Answer 1

a free open source Relational Database Management System, MySQL, SQL Server (Microsoft), Oracle (Oracle Corporation)

Question 2

What are some advantages of learning a relational database?

Answer 2

they are the most widely used kind of database

Question 3

What is one way to see if PostgreSQL is running?

Answer 3

sudo service postgresql status or top

Question 4

What is a database schema?

Answer 4

a description of how data should be structured

Question 5

What is a table?

Answer 5

a list of rows having the same set of attributes

Question 6

What is a row?

Answer 6

all of the data for an individual entry

Question 7

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

Answer 7

Structured Query Language, the primary way of interacting with relational databases, declarative programming language (like HTML and CSS)

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 “column” = ‘value’

Question 10

What are the benefits of formatting your SQL?

Answer 10

readability, style consistency

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

order by “column” (desc)

Question 15

How do you add a row to a SQL table?

Answer 15

insert into “table” (“column”)

values (‘value’)

Question 16

What is a tuple?

Answer 16

a list of values

Question 17

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

Answer 17

specify 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 clause

Question 19

How do you update rows in a database table?

Answer 19

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

Question 20

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

Answer 20

if where clause isn’t used, all rows would be updated

Question 21

How do you delete rows from a database table?

Answer 21

delete from “table”

where “column” = ‘value’

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

a column that links tables together

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

create an alias by using as keyword

select “column” as “alias”

Question 26

What are some examples of aggregate functions?

Answer 26

max( ), count( ), min( ), sum( )

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