PostgreSQL

Question 1

What is PostgreSQL and what are some alternative relational databases?

Answer 1

o Open source Relational Database Management System (RDBMS)

o Alternative RDBMS include:
Proprietary (pay money to use) - Oracle
Open Source (like postgres) - MySQL

Question 2

What are some advantages of learning a relational database?

Answer 2

o Widely used
o They support good guarantees about data integrity
o Store and modify data in a way that makes data corruption unlikely
o Many relational databases are driven by almost the same language

Question 3

What is one way to see if PostgreSQL is running?

Answer 3

o sudo service postgresql status

o top

Question 4

What is a database schema?

Answer 4

o Rules for how a data gets stored

o Collection of tables & their structure

Question 5

What is a table?

Answer 5

o Data stored in relations

o A list of rows that have the same set of attributes

Question 6

What is a row?

Answer 6

o A distinct record in a table

o A list of attributes and every row in the table has the same attributes

Question 7

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

Answer 7

o Structured Query Language (SQL) – primary way of interacting with relational databases (by retrieving, creating and manipulating data).

o SQL is a declarative programming language (unlike JS which is imperative)

Question 8

How do you retrieve specific columns from a database table?

Answer 8

select “attributeName”

from “tableName”

Question 9

How do you filter rows based on some specific criteria?

Answer 9

where “attributeName” = ‘value’

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

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

Question 15

How do you add a row to a SQL table?

Answer 15

insert into “tableName” (“attributeName”, . . .)

values (‘value’, ‘value’, . . . );

Question 16

What is a tuple?

Answer 16

A list of values (one line of values is “one tuple”)

Question 17

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

Answer 17

values (‘value’, ‘value’, . . . ),
values (‘value’, ‘value’, . . . )

(You add multiple tuples separated by a comma)

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 “tableName”

set “attributeName” = ‘newValue’;

Question 20

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

Answer 20

To target specific rows

Question 21

How do you delete rows from a database table?

Answer 21

delete from “tableName”

where “attributeName” = ‘value’

Question 22

How do you accidentally delete all rows from a table?

Answer 22

If you only write ‘delete from “tableName”’ WITHOUT A WHERE CLAUSE

Question 23

What is a foreign key?

Answer 23

A column present in one or more tables that links those tables together

Question 24

How do you join two SQL tables?

Answer 24

join “tableName” using (“foreignkey”)

Question 25

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

Answer 25

“columnOrTableName” as “newName”

Question 26

What are some examples of aggregate functions?

Answer 26

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

Question 27

What is the purpose of a group by clause?

Answer 27

To separate rows into groups based on a criteria