SELECT

What do we use SQL commands for? 

A common use is to select data from the tables located in a database. Immediately, we see two keywords: we need to SELECT information FROM a table.

we have the most basic SQL query structure:

SELECT "column_name" FROM "table_name";

There are three ways we can retrieve data from a table:

• Retrieve one column
• Retrieve multiple columns
• Retrieve all columns

Let's use the following table to illustrate all three cases:

Table Store_Information

Store_Name	Sales	Txn_Date
Los Angeles	1500	Jan-05-1999
San Diego	250	Jan-07-1999
Los Angeles	300	Jan-08-1999
Boston	700	Jan-08-1999

Select One Column

To select a single column, we specify the column name between SELECT and FROM as follows:

SELECT Store_Name FROM Store_Information;

Result:

Store_Name
--------------
Los Angeles
San Diego
Los Angeles

Boston

Select Multiple Columns

We can use the SELECT statement to retrieve more than one column. To select Store_Name and Sales columns from Store_Information, we use the following 

SQL:

SELECT Store_Name, Sales FROM Store_Information;

Result:

Store_Name	Sales
Los Angeles	1500
San Diego	250
Los Angeles	300
Boston	700

Select All Columns

There are two ways to select all columns from a table. The first is to list the column name of each column. The second, and the easier, way is to use the symbol *. For example, to select all columns from Store_Information, we issue the following SQL:

SELECT * FROM Store_Information;

Result:

Store_Name Sales Txn_Date

Los Angeles 1500 Jan-05-1999

San Diego          250 Jan-07-1999

Los Angeles  300 Jan-08-1999

Boston          700 Jan-08-1999