SELECT * FROM table_name

SELECT * FROM HumanResources.Employee

Never use: SELECT * FROM - in production code.

Reason:

1. COLUMNS can vary. Addition or removal of columns affect client application using them.
2. Network traffic - No need to select all the information, if you need only very few.

Operator	Description
!=	Tests two expressions not being equal to each other.
!>	Tests whether the left condition is less than or equal to (i.e., not greater than) the condition on the right.
!<	Tests whether the left condition is greater than or equal to (i.e., not less than) the condition on the right.
<	Tests the left condition as less than the right condition.
<=	Tests the left condition as less than or equal to the right condition.
<>	Tests two expressions not being equal to each other.
=	Tests equality between two expressions.
>	Tests the left condition being greater than the expression to the right.
>=	Tests the left condition being greater than or equal to the expression to the right.

SELECT * FROM HumanResources.Employee

WHERE JobTitle='SALES Representative'

WHERE - can be combined with AND and OR 

SELECT 

FirstName

,LastName AS [Surname]

FROM

Person.Person

COLUMN ALIAS

SELECT BusinessEntityID AS EmployeeID

       ,VacationHours + SickLeaveHours AS [TotalHolidaysAvailable]
FROM HumanResources.Employee;

TABLE ALIAS:

SELECT E.BirthDate FROM HumanResources.Employee AS E