SQL SELECT

SQL > SQL Commands > 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. (Note that a table is a container that resides in the database where the data is stored. For more information about how to manipulate tables, go to the Table Manipulation Section). Hence 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