SQL

Question 1

What is PostgreSQL and what are some alternative relational databases?

Answer 1

It is a relation database management system . other relational databases include MySQL, SQL Server by Microsoft, and Oracle

Question 2

What are some advantages of learning a relational database?

Answer 2

portable skill, and used everywhere

Question 3

What is one way to see if PostgreSQL is running?

Answer 3

top command,

Question 4

What is a database schema?

Answer 4

A collection of tables

Question 5

What is a table?

Answer 5

in terms of relational databases, a table is known as a relation which stores data in rows and attributes(columns)

Question 6

What is a row?

Answer 6

a row is an instance of a record in that table, that has a set of attributes

Question 7

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

Answer 7

Structured Query Language: it is declarative vs imperative like JavaScript.

Question 8

How do you retrieve specific columns from a database table?

Answer 8

select “columnName”

Question 9

How do you filter rows based on some specific criteria?

Answer 9

where “column” (=,, !=) ‘criteria’

Question 10

What are the benefits of formatting your SQL?

Answer 10

readabililty

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 “criteria” (desc)

- ascending by default

Question 15

How do you add a row to a SQL table?

Answer 15

insert into “table” (‘column’(s))

values (‘value’(s))

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

groups in parenthesis separated by commas

Question 18

How to 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 “table”
set “column” = ‘value’
where “value” = ‘value’

Question 20

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

Answer 20

without where, it would update all values in that column

Question 21

How do you delete rows from a database table?

Answer 21

delete from “tableName”

where “column” = ‘value’

Question 22

How do you accidentally delete all rows from a table?

Answer 22

delete from “tableName”

without specifying where

Question 23

What is a foreign key?

Answer 23

a column that links the values from one table to another

Question 24

How do you join two SQL tables?

Answer 24

join keyword
select *
from “table”
join “table2” using (“foreignKey”);

Question 25

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

Answer 25

(for columns) : select “table”.”column” as “name”

(for tables) : from “table” as “name”

Question 26

What are some examples of aggregate functions?

Answer 26

count(), sum(), avg()

Question 27

What is the purpose of a group by clause?

Answer 27

used to separate different rows into groups