SQL

Question 1

What is PostgreSQL and what are some alternative relational databases?

Answer 1

o An open-source relational database management system

o MySQL, SQL Server, Oracle

Question 2

What are some advantages of learning a relational database?

Answer 2

They are widely used so most web developers will work with one at least a little during their career

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; it defines how the data should be organized

Question 5

What is a table(relation)?

Answer 5

A collection of related data

Question 6

What is a row(tuple)?

Answer 6

A single data item in a table

Question 7

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

Answer 7

A domain-specific declarative language used for managing data held in relational database management systems

Question 8

How do you retrieve specific columns from a database table?

Answer 8

select statement

Question 9

How do you filter rows based on some specific criteria?

Answer 9

where clause

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

*

Question 14

How do you control the sort order of a result set?

Answer 14

order by clause (ascending is default if descending add desc)

Question 15

How do you update rows in a database table?

Answer 15

update statement

Question 16

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

Answer 16

If you don’t, will update all rows

Question 17

How do you delete rows from a database table?

Answer 17

delete statement

Question 18

How do you accidentally delete all rows from a table?

Answer 18

Don’t include a where clause

Question 19

What is a foreign key?

Answer 19

A column value that links to another table

Question 20

How do you join two SQL tables?

Answer 20

join clause

Question 21

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

Answer 21

as keyword (aliasing)

Question 22

What are some examples of aggregate functions?

Answer 22

count, max, min, avg, sum

Question 23

What is the purpose of a group by clause?

Answer 23

separate rows into groups and perform aggregate functions on those groups of rows