postgres & sql

Question 1

Why do we use databases in Web development?

Answer 1

for applications to quickly retrieve or store complex data in an organized fashion and to share data to other users and provide a centralized location for application data.

Question 2

What is PostgreSQL and what are some alternative relational databases?

Answer 2

a free open source database Relational Database Management System (RDBMS). some alternatives are MySQL, SQL Server, and Oracle.

Question 3

What are some advantages of learning a relational database?

Answer 3

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

Question 4

What is one way to see if PostgreSQL is running?

Answer 4

sudo (super user do) service postgresql status

Question 5

What is a database schema?

Answer 5

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

Question 6

What is a table?

Answer 6

Relational databases store data in relations. a collection of objects that are the same shape.

Question 7

What is a row?

Answer 7

a table each having the same set of attributes. an object or item

Question 8

What is an attribute and what other names are used to describe them?

Answer 8

column, key

Question 9

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

Answer 9

its a declarative programming language and you just tell it what you want not how.

Question 10

How do you retrieve specific columns from a database table?

Answer 10

by using the select and column names after select in double quotes.

Question 11

How do you filter rows based on some specific criteria?

Answer 11

by using the ‘where’ clause and any type of expression and the data type value is surrounded by single quotes only if its a string

Question 12

What are the benefits of formatting your SQL?

Answer 12

to make it more readability

Question 13

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

Answer 13

= , < , > , !=

Question 14

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

Answer 14

use the limit keyword

Question 15

How do you retrieve all columns from a database table?

Answer 15

use the * to get all columns

Question 16

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

Answer 16

use the order by keyword and column name in double quotes and to get it in descending order use keyword desc after the column name

Question 17

How do you add a row to a SQL table?

Question 18

What is a tuple?

Question 19

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

Question 20

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

Question 21

How do you update rows in a database table?

Question 22

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

Question 23

How do you delete rows from a database table?

Question 24

How do you accidentally delete all rows from a table?

Question 25

What is a foreign key?

Answer 25

a key that references back to the primary key of another table

Question 26

How do you join two SQL tables?

Answer 26

keyword join, table.name, keyword using, and column.name

Question 27

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

Answer 27

using the keyword as

Question 28

What are some examples of aggregate functions?

Answer 28

count(), avg(), sum(), min(), max(), etc

Question 29

What is the purpose of a 'group by' clause?

Answer 29

so you can have everything in a group