How to create a SQL query?

Table users_signin

id int(11)
oauth_provider enum(", 'linkedin')
oauth_uid varchar(100)
first_name varchar(50)
last_name varchar(50)
email varchar(100)
location varchar(255)
picture varchar(255)
profile_url varchar(255)
created datetime
industry varchar(255)

Table users_positions

users_id int(11)
unique_id int(11)
location varchar(255)
title varchar(255)
startDate varchar(255)
company_id int(11)

users_id connection with users_signin id
company_id - communication with users_company id

Table users_company

id int(11)
unique_id int(11)
industry varchar(255)
name varchar(255)
type varchar(255)