SQL 101 3: SELECT and FROM

This is the third in my series of posts designed to teach people the basics of SQL and it’s use in interrogating databases.

The SELECT Clause
The SELECT clause is used to define the columns that are to be displayed in the Results Table for each record that satisfies the query conditions. If more than one Column is specified the field names must be separated with commas. If only one Column is specified, no separator is required. For example:

SELECT CUS_PRIMARYKEY,CUS_CODE
or
SELECT CUS_CODE


The FROM Clause
The FROM clause is used to define the Table from which the records are to be selected. The FROM clause normally follows the SELECT clause, and in order to keep the structure of the query clear, it can often be found entered on a separate line. For Example:

SELECT CUS_PRIMARYKEY,CUS_CODE
FROM GUSER.F_CUSTOMER

This means that the Columns Primary Key and Customer Code are to be retrieved from the table F_CUSTOMER. If more than one Table is to be used in a query (using a SQL ‘Join’ which is a technique for linking related tables),  the Table names must be separated by a comma. For Example:

SELECT CUS_PRIMARYKEY,CUS_CODE,SOH_NET
FROM GUSER.F_CUSTOMER, GUSER.F_SOHDR
WHERE

Tomorrow: The WHERE Clause.

"Most folks are about as happy as they make up their minds to be." - Abraham Lincoln