PostgreSQL

Question 1

What is PostgreSQL and what are some alternative relational databases?

Answer 1

open source object-relational database management system; mySQL, Oracle, Microsoft SQL server

Question 2

What are some advantages of learning a relational database?

Answer 2

Relational databases are arguably the most widely used kind of database. Many web developers work with a relational database at least a little bit during their career

Question 3

What is one way to see if PostgreSQL is running?

Answer 3

command sudo service postgresql status

Question 4

What is a database schema?

Answer 4

a collection of tables that defines how the data in a relational database should be organized

Question 5

What is a table?

Answer 5

a list of rows each having the same set of attributes;a database table is sort of like a spreadsheet where each row is a record in that spreadsheet

Question 6

What is a row?

Answer 6

single structured data item in a table

Question 7

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

Answer 7

primary way of interacting with relational databases. It is a powerful way of retrieving, creating, and manipulating data in a relational database; JavaScript is imperative and SQL is declarative

Question 8

How do you retrieve specific columns from a database table?

Answer 8

select “columnName”

from “tableName”;

Question 9

How do you filter rows based on some specific criteria?

Answer 9

where “columnName” = ‘specific description’

Question 10

What are the benefits of formatting your SQL?

Answer 10

consistent style helps with 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 number; limit clause always comes last

Question 13

How do you retrieve all columns from a database table?

Answer 13

select *

from “tableName”

Question 14

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

Answer 14

order by clause ; default it ascending order; if specified can use descending order; order by “whatever” desc

Question 15

How do you add a row to a SQL table?

Answer 15

insert into “tableName”(“columnName”)

values (‘columnValue’);

Question 16

What is a tuple?

Answer 16

the list of values being inserted in parenthesis

Question 17

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

Answer 17

insert into “tableName”(“columnName”)
values (‘this’),
(‘that’)

Question 18

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

Answer 18

use returning clause;
insert into “tableName”(“columnName”)
values (‘columnValue’)
returning *;

Question 19

How do you update rows in a database table?

Answer 19

update “tableName”
set “columnName” = ‘new value’
where “columnName” = ‘value’

Question 20

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

Answer 20

to update specific statments at target specified in where clause

Question 21

How do you delete rows from a database table?

Answer 21

delete from “tableName”

where “columnName” = ‘specific’

Question 22

How do you accidentally delete all rows from a table?

Answer 22

omitting the where clause

Question 23

What is a foreign key?

Answer 23

when a column in a table specifically refers to values in a different table with the same column name

Question 24

How do you join two SQL tables?

Answer 24

select “tableName”.”columnName”
“otherTableName”.”columnName”
from “tableName”
join “otherTableName” using (“columnNameInCommon”);

Question 25

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

Answer 25

select “tableName”.”columnName” as “newName”

Question 26

What are some examples of aggregate functions?

Answer 26

count( ), sum ( ), avg ( ), max ( )

Question 27

What is the purpose of a group by clause?

Answer 27

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