Chapter 6 Overview of Data Manipulation

Table of Contents

To manipulate data in an ALLBASE/SQL DBEnvironment, you use one of the following SQL commands:

SELECT: to retrieve one or more rows from one or more tables.
INSERT: to insert one or more rows into a single table.
DELETE: to delete one or more rows from a single table.
UPDATE: to change the value of one or more columns in one or more rows in a single table.

Three techniques exist for using these commands in a program:

In simple data manipulation, you retrieve or insert single rows or you delete or update one or more rows based on a specific criterion.
In sequential table processing, you operate on a set of rows, one row at a time, using a cursor. A cursor is a pointer that identifies one row in the set of rows, called the active set. You move through the active set, retrieving a row at a time and optionally updating or deleting it.
In dynamic operations, you preprocess SQL commands at runtime, as when the program accepts data manipulation commands from a user.

Table 6-1 summarizes which data manipulation commands can be used in each technique. Note that the FETCH command is included in this table, since it must be used when you manipulate data using a cursor.

Table 6-1 How Data Manipulation Commands May Be Used

	USABLE SQL COMMANDS
TYPE OF OPERATION	SELECT	FETCH	INSERT	DELETE	UPDATE	DELETE WHERE CURRENT	UPDATE WHERE CURRENT
Simple	X		X	X	X
Sequential	X	X				X	X
Dynamic		X	X	X	X

The remainder of this chapter briefly examines each of the three data manipulation techniques (each technique is discussed in detail in Chapters 7 through 9) and introduces the use of a cursor for data manipulation. First, however, this chapter addresses the query, or the description of data you want to retrieve. Queries are fundamental to ALLBASE/SQL data manipulation because some of the elements of a query are also used to describe and limit data when you update or delete it. In addition, it is common programming practice to retrieve and display rows prior to changing or deleting them.

Chapter 6 Overview of Data Manipulation

Technical documentation

» Table of Contents

» Index