SQL Server 2017 Developer's Guide

Core Transact-SQL SELECT statement elements

The simplest query to retrieve the data that you can write includes the SELECT and the FROM clauses. In the SELECT clause, you can use the star character (*), literally SELECT *, to denote that you need all columns from a table in the result set. The following code switches to the WideWorldImportersDW database context and selects all data from the Dimension.Customer table:

USE WideWorldImportersDW; 
SELECT * 
FROM Dimension.Customer; 

The code returns 403 rows, all customers with all columns.

Using SELECT * is not recommended in production. Such queries can return an unexpected result when the table structure changes, and is also not suitable for good optimization.

Better than using SELECT * is to ...