postgresQL

Question 1

What is postgreSQL and what are some alternative relational databases?

Answer 1

open source relational database management system

Question 2

What are some advantages of learning a relational database?

Answer 2

most apps use data

easier to work with data that is related

Question 3

What is one way to see if postgreSQL is running?

Answer 3

top command in CLI

sudo service postgresql status command in CLI

Question 4

What is a database schema?

Answer 4

a collection of tables

Question 5

What is a table?

Answer 5

a table is a list of rows each having the same set of attributes(aka columns)

Question 6

What is a row?

Answer 6

each row is a single record of data in the table

Question 7

what is SQL and how is it different from languages like JS?

Answer 7

sql is a language used to interact with relational databases

sql is declarative language rather than imperative like JS

you describe the result you want rather than what and how to do it like with JS

Question 8

How do you retrieve specific columns from a database table?

Answer 8

use the “select” keyword and the string version of the columns in double quotes you wish to see separated by commas

Question 9

How do you filter rows based on some specific criteria?

Answer 9

use the “where” statement

“columnName” operator (‘dataValue’)

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 followed by num value

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 “columnName” desc/asc

Question 15

How do you add a row to a SQL table?

Answer 15

insert into “table” (“columnName”, “columnName)
values (‘firstName’, ‘lastName’)
returning *;

Question 16

What is a tuple?

Answer 16

a list of values in sql

Question 17

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

Answer 17

multiple tuple rows with commas separating the tuples

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

using the “update”, “set”, and “where” keywords

Question 20

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

Answer 20

So that the code knows what row needs to be updated

Question 21

how do you delete rows from a database table?

Answer 21

using the clause “delete from” “table name” and “where”

Question 22

How do you accidentally delete all rows from a table?

Answer 22

delete from “table”;

Question 23

What does ACID stand for as it pertains to transactions?

Answer 23

Atomicity - all changes to data are performed as if they are a single operation. All changes are performed or none are

Consistency - data is in a consistent state when a transaction starts and when it ends

Isolation - the intermediate state of a transaction is invisible to other transactions

Durability - after successful transaction completes, changes to data persist and are not undone, event in the event of a system failure.

Question 24

3 commands to use with transactions

“transactions help with manipulating databases in a safe mode”

Answer 24

begin
commit
rollback

Question 25

what is a foreign key?

Answer 25

a column title that links data from another table to that table

column values need to be the same

Question 26

How do you join two sql tables?

Answer 26

select *
from “table”
join “table2” using (“foreign key from table 1”);

Question 27

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

Answer 27

using aliasing with the “as” keyword

doesn’t alter the name permanently

Question 28

What are some examples of aggregate functions?

Answer 28

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

Question 29

What is the purpose of a “group by” clause?

Answer 29

to sub-divide rows in a result set into groups and then perform the aggregate on each group