Postgres

Question 1

What is PostgreSQL and what are some alternative relational databases?

Answer 1

PostgreSQL is a free open-source relational database management system

PostgreSQL is a relational database system that is free and open source. Some alternatives are MySQL, SQL Server, and Oracle.

Question 2

What are some advantages of learning a relational database?

Answer 2

They’re the most widely used type of database.

They support good guarantees about data integrity.

They can store and modify data in a way that makes corruption as unlikely as possible.

They are good for storing related data. They can store and modify data in a way that makes data corruption as unlikely as possible. Also, they are arguably the most widely used kind of database.

Simple Model. Flat

Question 3

What is one way to see if PostgreSQL is running?

Answer 3

by running ‘sudo service postgresql status’ command
By having a 2nd terminal open and running the top command to monitor the open processes.

sudo service postgresql status / top

1. Use the terminal command sudo service postgresql status.
2. Check use the terminal top command to see if postgres is running

Question 4

What is a database schema?

Answer 4

A collection of tables in a database.

Question 5

What is a table?

Answer 5

A list of rows and columns that store data in relations.

Question 6

What is a row?

Answer 6

A row is an entry in a table and every row contains the same set of attributes

A single instance of a record within a table.

Question 7

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

Answer 7

SQL is a declarative programming language. Instead of telling the code what to do, you describe the results you want.

Question 8

How do you retrieve specific columns from a database table?

Answer 8

Start with the select keyword.

The select keyword is followed by a comma-separated list of column names, each surrounded by “double quotes”.

e.g: select “firstName”,
“lastName”

By using the select keyword follow by one or more column name wrapped in double quotes.

Question 9

How do you filter rows based on some specific criteria?

Answer 9

By using the where clause

Question 10

What are the benefits of formatting your SQL?

Answer 10

For consistent style and 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

asterisk

Question 14

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

Answer 14

order by “column”; desc if you want it in descending order
Use the order by keyword followed by the column you want to order by in “double quotes.” order will be in ascending order by default - add desc keyword after “specified column” to sort in descending order.

Question 15

How do you add a row to a SQL table?

Answer 15

insert statement insert into clause followed by the “table” then (column names separated by commas)

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

By using multiple tuples which are separated by commas but still follow the same order as the columns they belong to.

Question 18

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

Answer 18

using the returning keyword along with the star/asterisk

Question 19

How do you update rows in a database table?

Answer 19

update clause followed by name of table. then the set clause followed by the column that needs updating followed by an equal operator then the value of the desired update

Question 20

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

Answer 20

If a where clause is not used, the whole entire table is updated instead of just the targeted/desired data.

Question 21

How do you delete rows from a database table?

Answer 21

delete from clause followed by the table

Question 22

How do you accidentally delete all rows from a table?

Answer 22

By not specifying what to delete with the where clause

Question 23

What is a foreign key?

Answer 23

a key used to link two tables together

A column that links one table to another

Question 24

How do you join two SQL tables?

Answer 24

from clause followed by the table name and then the join clause followed by the table name as well and then the using keyword to specify the foreign key.

Question 25

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

Answer 25

By creating an Alias name with the as keyword

Question 26

What are some examples of aggregate functions?

Answer 26

max(): Finds max number
avg(): Finds average
count(*): Counts number of rows
min()
sum()
every()
look into JSON aggregate functions

Question 27

What is the purpose of a group by clause?

Answer 27

Separates rows into groups to perform aggregate functions.