postgres

Question 1

What is PostgreSQL and what are some alternative relational databases?

Answer 1

PostgreSQL is a powerful, free, open source Relational Database Management System (RDBMS).

some altenratives are SQL server, MySQL, oracle

Question 2

What are some advantages of learning a relational database?

Answer 2

A quality of many relational databases is that they support good guarantees about data integrity.
Relational databases are arguably the most widely used kind of database

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 is called a schema. A schema defines how the data in a relational database should be organized. In relational databases, you typically have to define your schema up front and the database server will make sure that any data being written to the database conforms to that schema.

Question 5

What is a table?

Answer 5

relational databases store data in relations, commonly referred to as tables. A table is a list of rows each having the same set of attributes. columns are often referred to as attributes.

Question 6

What is a row?

Answer 6

rows are the single record of data

Question 7

What is SQL and how is it different from languages like JavaScript?
How do you retrieve specific columns from a database table?
How do you filter rows based on some specific criteria?
What are the benefits of formatting your SQL?
What are four comparison operators that can be used in a where clause?
How do you limit the number of rows returned in a result set?
How do you retrieve all columns from a database table?
How do you control the sort order of a result set?

Answer 7

Structured Query Language (SQL) is the primary way of interacting with relational databases. It is a powerful way of retrieving, creating, and manipulating data in a relational database. SQL is a declarative language, not imperative. imperative you have to tell each step.

Question 8

How do you filter rows based on some specific criteria?

Answer 8

select “attributeName”,

from “tableName”

Question 9

how do you filter rows based on specific criteria?

Answer 9

select “attributes”,
from “tablename,
where “attribute” = ‘alvin’;

Question 10

What are the benefits of formatting your SQL?

Answer 10

cleaner easier to read

Question 11

What are four comparison operators that can be used in a where clause?

Answer 11

= < > between

Question 12

How do you limit the number of rows returned in a result set?

Answer 12

use the limit clause

Question 13

How do you retrieve all columns from a database table?

Answer 13

select *

Question 14

How do you add a row to a SQL table?

Answer 14

insert into “products” (“name”, “description”, “price”, “category”)
values (‘Ostrich Pillow’, ‘Feel comfy and cozy!’, 99, ‘self care’),
(‘Tater Mitts’, ‘Scrub some taters!’, 6, ‘cooking’)
returning *;

Question 15

What is a tuple?

Answer 15

In SQL, a list of values is referred to as a tuple.

Question 16

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

Answer 16

insert into “products” (“name”, “description”, “price”, “category”)
values (‘Ostrich Pillow’, ‘Feel comfy and cozy!’, 99, ‘self care’),
(‘Tater Mitts’, ‘Scrub some taters!’, 6, ‘cooking’)
returning *;

Question 17

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

Answer 17

returning *

Question 18

How do you update rows in a database table?

Answer 18

update “products”
set “price” = 100
where “productId” = 24;

Question 19

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

Answer 19

it would update every row in the table!

Question 20

How do you delete rows from a database table?

Answer 20

delete from “products”
where “productId” = 24
returning *;

Question 21

How do you accidentally delete all rows from a table?

Answer 21

delete from “products”;

Question 22

What is a foreign key?

Answer 22

column in a table that has values that are constrained to match another column in another table.

Question 23

How do you join two SQL tables?

Answer 23

select “products”.”name” as “product”,
“suppliers”.”name” as “supplier”
from “products”
join “suppliers” using (“supplierId”);

Question 24

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

Answer 24

select "p"."name" as "product",
       "p"."category",
       "s"."name" as "supplier",
       "s"."state"
  from "products" as "p"
  join "suppliers" as "s" using ("supplierId");

Question 25

What are some examples of aggregate functions? convert a lot of values into a single value.

Answer 25

sum
count
avg

Question 26

What is the purpose of a group by clause?

Answer 26

you want to separate rows into groups and perform aggregate functions on those groups of rows