sql select

Question 1

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

Answer 1

Structured Query Language is a way of interacting with relational databases to retrieve, create and manipulate data. SQL is a declarative programming language, programmers describe the result like HTML and CSS.

Question 2

How do you retrieve specific columns from a database table?

Answer 2

select “string”, “string” from “table to retrieve from”;
to select all use select * from “products”

column double quotes

Question 3

How do you filter rows based on some specific criteria?

Answer 3

using the where clause.
where double quotes comparison operator single quote

select “productID”, “name”, “price”
from “products”
where “category” = ‘cleaning’;

Question 4

What are the benefits of formatting your SQL?

Answer 4

makes it easier to read and access data

Question 5

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

Answer 5

=
!=
<
>

Question 6

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

Answer 6

with the Limit clause

Question 7

How do you retrieve all columns from a database table?

Answer 7

select *

Question 8

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

Answer 8

order by “price” desc (descending)

limit 1;

Question 9

How do you add a row to a SQL table?

Answer 9

insert statement
insert into “ “ ( “ “ )
values ( ‘ ‘ ) ;

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

specify more than one tuple of values separated by commas:

values (‘Ostrich Pillow’, ‘Feel comfy and cozy!’, 99, ‘self care’),
(‘Tater Mitts’, ‘Scrub some taters!’, 6, ‘cooking’)

Question 12

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

Answer 12

returning *

Question 13

How do you update rows in a database table?

Answer 13

update clause:

update “products”
set “price” = 200,
“name” = ‘Super ShakeWeight’,
“description” = ‘Makes you ULTRA strong!’
where “productId” = 24;

Question 14

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

Answer 14

otherwise all of the rows will update

Question 15

How do you delete rows from a database table?

Answer 15

delete clause

delete from “products”
where “category” = ‘cleaning’
and “price” < 20
returning *;

Question 16

How do you accidentally delete all rows from a table?

Answer 16

by not specifying a where

Question 17

What is a foreign key?

Answer 17

a column that links one table to another, common property or column between two tables.

Question 18

How do you join two SQL tables?

Answer 18

Select statement
From “table 1”
join “table 2” using (“foreign key”);

Question 19

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

Answer 19

can alias column names using the

Question 20

What are some examples of aggregate functions?

Answer 20

max(), avg(), count(), min(), sum(), and every()

select “category”,
avg(“price”) as “averagePrice”
from “products”
group by “category”;

Question 21

What is the purpose of a group by clause?

Answer 21

groups all of the data together