PostgreSQL

Question 1

What is PostgreSQL and what are some alternative relational databases?

Answer 1

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

The most widely used kind of database. SQL is a very useful skill to have. Data corruption is very unlikely to happen in a relational database.

Question 3

What is one way to see if PostgreSQL is running?

Answer 3

By having a 2nd terminal open and running the top command to monitor the open processes.

Question 4

What is a database schema?

Answer 4

A schema defines how the data in a relational database is organized.

Question 5

What is a table?

Answer 5

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

Question 6

What is a row?

Answer 6

A row is each individual record or entry that has a set of attributes/columns.

Question 7

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

Answer 7

SQLis considered a declarative language. Meaning programmers can declare their intent and the output is the desired result.

Question 8

How do you retrieve specific columns from a database table?

Answer 8

select “name of column”

Question 9

How do you filter rows based on some specific criteria?

Answer 9

where “column” (operator) ‘criteria’

Question 10

What are the benefits of formatting your SQL?

Answer 10

Readability. For the business side of things to interpret the data. Consistency.

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 (number)

Question 13

How do you retrieve all columns from a database table?

Answer 13

select asterisk*

Question 14

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

Answer 14

using order by “column”

Question 15

How do you add a row to a SQL table?

Answer 15

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. The values being wrapped in parenthesis that are in the same order as the columns they belong to.

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

if a where clause is not used, the entire table will be deleted.

Question 23

What is a foreign key?

Answer 23

a foreign key is a column that is originally defined/unique in a table and then used in another table as a reference to relate to each table.

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

when selecting columns, the as keyword is used after the name of the columns stated.

Question 26

What are some examples of aggregate functions?

Answer 26

max/min, avg, count, sum

Question 27

What is the purpose of a group by clause?

Answer 27

It allows the grouping of rows so the aggregate functions can be focused on only them. Instead of focusing on every row in the table.