LFZ Quiz questions (Senior #3)

Question 1

(postgres-intro)

What is PostgreSQL and what are some alternative relational databases?

Answer 1

PostgreSQL is one of the relational database. Other popular relational databases include MySQL (also free), MariaDB, MongoDB, SQL Server by Microsoft, and Oracle by Oracle Corporation.

Question 2

(postgres-intro)

What are some advantages of learning a relational database?

Answer 2

Many problem domains can be modeled well using a relational database. If you are storing related data, then a relational database is probably a good first choice!
This model organizes data into one or more tables (or “relations”) of columns and rows, with a unique key identifying each row.

Question 3

(postgres-intro)

What is one way to see if PostgreSQL is running?

Answer 3

We can use a command ‘top’ to see the process of postgres

Question 4

(postgres-database)

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. bunch of tables.

Question 5

(postgres-database)

What is a table?

Answer 5

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

Question 6

(postgres-database)

What is a row?

Answer 6

A row represents a single, implicitly structured data item in a table.
Whereas, Attributes are commonly referred to as columns.

Question 7

(sql-select)

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

Answer 7

SQL is Structured Query Language and declarative programming language. In declarative languages, programmers describe the results they want and the programming environment comes up with its own plan for getting those results.

Question 8

(sql-select)

How do you retrieve specific columns from a database table?

Answer 8

The select keyword is followed by specific column’s name

Question 9

(sql-select)

How do you filter rows based on some specific criteria?

Answer 9

We can use a keyword ‘where’ and “column name” = ‘criteria’

Question 10

(sql-select)

What are the benefits of formatting your SQL?

Answer 10

It’s easy to read and alter values.

dynamically generate a plan of action to perform the programmer’s commands as efficiently as possible.

Question 11

(sql-select)

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

Answer 11

=, , !=, <=, >=, etc

Question 12

(sql-select)

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

Answer 12

We can use limit keyword and number

ex) limit 5

Question 13

(sql-select)

How do you retrieve all columns from a database table?

Answer 13

select * from “table name”

Question 14

(sql-select)

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

Answer 14

We can use order by keyword

ex) order by “column name” desc / asc

Question 15

(sql-insert)

How do you add a row to a SQL table?

Answer 15

ex)
insert into “products” (“name”, “description”, “price”, “category”)
values (‘Ostrich Pillow’, ‘Feel comfy and cozy!’, 99, ‘self care’);

Question 16

(sql-insert)

What is a tuple?

Answer 16

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

Question 17

(sql-insert)

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

Answer 17

Data rows can be batch inserted into a database table by specifying more than one tuple of values, separated by commas.
ex)
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 18

(sql-update)

How do you update rows in a database table?

Answer 18

We can use update, set, where clauses.
ex)
update "products"
   set "price" = 100
 where "productId" = 24;

Question 19

(sql-update)

How do you update rows in a database table?

Answer 19

We can use update, set, where clauses.
ex)
update "products"
   set "price" = 100
 where "productId" = 24;

Question 20

(sql-delete)

How do you delete rows from a database table?

Answer 20

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

Question 21

(sql-delete)

How do you accidentally delete all rows from a table?

Answer 21

delete from “table name”;

without where statement

Question 22

(sql-delete)

How do you accidentally delete all rows from a table?

Answer 22

delete from “table name”;

without where clause

Question 23

(sql-join)

What is a foreign key?

Answer 23

Other table’s primary key can be uses as a column attribute to make a relation between two tables.

Question 24

(sql-join)

How do you join two SQL tables?

Answer 24

select *
from “products”
join “suppliers” using (“supplierId”);

Question 25

(sql-join)

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

Answer 25

We can use “as” clause .

Question 26

(sql-aggregates)

What are some examples of aggregate functions?

Answer 26

sum, count, avg, max, min

Question 27

(sql-aggregates)

What is the purpose of a group by clause?

Answer 27

It divides rows into groups and applies an aggregate function on each.