SQL Select

Question 1

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

Answer 1

SQL (Structured Query Language) is a declarative programming language for querying databases. SQL is the primary way of interacting with relational databases. It is a powerful way of retrieving, creating, and manipulating data in a relational database.

SQL is a 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 2

How do you retrieve specific columns from a database table?

Answer 2

Using the select statement, followed by a comma-separated list of column names, each surrounded by double quotes.

select “name”,
“price”
from “products”;

• The column names are followed by a from clause specifying which table to retrieve the data from.
• The query must end in a ; semicolon.
  SQL keywords such as select and from are not case-sensitive.
• SQL does not have to be indented, but you should do it anyway for consistent style and therefore readability.

Question 3

How do you filter rows based on some specific criteria?

Answer 3

This is done using a where clause.

select "productId",
       "name",
       "price"
  from "products"
 where "category" = 'cleaning';

Question 4

What are the benefits of formatting your SQL?

Answer 4

Consistent style and therefore readability

Question 5

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

Answer 5

Greater than “>”, less than “

Question 6

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

Answer 6

By using the “limit” clause followed by the number limit

select "name",
       "description"
  from "products"
 order by "price" desc
 limit 1;

Question 7

How do you retrieve all columns from a database table?

Answer 7

With select and the asterisk

select *
from “products”;

Question 8

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

Answer 8

By using the “order by” clause

select *
from “products”
order by “price”;