SQL

Question 1

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

Answer 1

Structured Query Language (SQL) is the primary way of interacting with relational databases. JS is imperative programming language and SQL is a declarative programming language

Question 2

How do you retrieve specific columns from a database table?

Answer 2

SELECT column name and FROM table name

Question 3

How do you filter rows based on some specific criteria?

Answer 3

select, from, and where keyword

Question 4

What are the benefits of formatting your SQL?

Answer 4

Helps us to make the queries more readable and easy to understand.

Question 4

What are the benefits of formatting your SQL?

Answer 4

Helps us to make the queries more readable and easy to understand.

Question 5

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

Answer 5

=, <, >, and !=

Question 6

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

Answer 6

use limit keyword and the number of rows

Question 7

How do you retrieve all columns from a database table?

Answer 7

select * from tableName

Question 8

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

Answer 8

order by “column name” desc/asc

Question 9

How do you add a row to a SQL table?

Answer 9

Insert into “tableName” (“columnName”)
values (‘value’)

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

Question 10

What is a tuple?

Answer 10

a list of values

Question 11

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

Answer 11

values (‘value’),
(‘value’)

insert into “products” (“name”)
values (‘Ostrich Pillow’),
(‘Tater Mitts’)
returning *;

Question 12

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

Answer 12

by using keyword returning *;

Question 13

How do you update rows in a database table?

Answer 13

update “tableName”
set “column/attribute” = ‘value’
where “selection” = ‘value’;

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

Question 14

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

Answer 14

to target specific rows so it does not update every row in the table

Question 15

How do you delete rows from a database table?

Answer 15

delete
from “table name”
where “columnName/attribute” = ‘value’

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

Question 16

How do you accidentally delete all rows from a table?

Answer 16

delete
from “tableName”;

Question 17

What is a foreign key?

Answer 17

Column that show up in multiple tables

Question 18

How do you join two SQL tables?

Answer 18

select “tableName”.”columnName”
from “tableName”
join “tableName” using (“columnName”);

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

Question 19

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

Answer 19

join “tableName” as “c” using (“customerId”)

“tableName”.”currentColumnName” as “newColumnName”

Question 20

What are some examples of aggregate functions?

Answer 20

An aggregate function performs a calculation on a set of values, and returns a single value. Ex: min(), sum(), and every(), max()

Question 21

What is the purpose of a group by clause?

Answer 21

the group the results of aggregate functions . It basically allows us to create our own collection of data within a collection of data