SQL

Question 1

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

Answer 1

SQL is way of interacting with relational databases and is different from JavaScript because it is a declarative programming languages. You also don’t really tell the computers what to do.

Question 2

How do you retrieve specific columns from a database table?

Answer 2

using select “column name or attributes”

Question 3

How do you filter rows based on some specific criteria?

Answer 3

you use where clause “column name” = the ‘row name’

Question 4

What are the benefits of formatting your SQL?

Answer 4

It makes your code easier to read and decipher

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 limit operator

Question 7

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

Answer 7

order by “column name” - by default it is ascending order and can make it descending by desc operator

Question 8

How do you retrieve all columns from a database table?

Answer 8

select *

Question 9

How do you add a row to a SQL table?

Answer 9

using insert keyword with what columns and values you want to insert

Question 10

What is a tuple?

Answer 10

list of values

Question 11

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

Answer 11

you specify more than one tuple of values, separated by commas

Question 12

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

Answer 12

using returning *

Question 13

How do you update rows in a database table?

Answer 13

use update statement with “file name” and set clause

Question 14

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

Answer 14

Without the where clause, set value will be updated to all rows

Question 15

How do you delete rows from a database table?

Answer 15

Use delete statement with where clause

Question 16

How do you accidentally delete all rows from a table?

Answer 16

delete from “file name”

Question 17

What is a foreign key?

Answer 17

foreign key links one table to another with same attributes

Question 18

How do you join two SQL tables?

Answer 18

using join clause with using keyword and attribute you want to join together

Question 19

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

Answer 19

using as keyword

Question 20

What are some examples of aggregate functions?

Answer 20

sum(), min(), every(), avg()

Question 21

What is the purpose of a group by clause?

Answer 21

To separate rows into groups and perform aggregate functions on those groups of rows