General Concepts

ALLBASE/SQL stores LONG column data in a database for later retrieval. LONG column data is not processed by ALLBASE/SQL. Any formatting, viewing, or other processing must be accomplished by means of your program. For example, you might use a graphics application to create an intricate graphic display (or set of graphic displays). You could then write a program in which you embed ALLBASE/SQL commands to store each graphics file in your database along with related data in a given row. Your graphics application could be called from another program, this time to select a row and display the graphic. The graphic could be displayed on the upper portion of a screen, with related data from the same row displayed on the lower portion of a screen. The related data in standard columns or LONG columns could be a graphics explanation or an entire chapter.

LONG column data can occupy a practically unlimited amount of space in the database, the maximum number of bytes being 2³¹-1 (or 2,147,483,647) per LONG column per row. Standard column data is restricted to 3996 bytes maximum.

The LONG specification is used with a given ALLBASE/SQL data type when you create the LONG column. Currently, LONG BINARY and LONG VARBINARY are available. Refer to the chapter on "Host Variables" for the details of BINARY and VARBINARY data types.

The concept of how LONG column data is stored in a row and retrieved differs from that of standard columns. Although LONG column data is associated with a particular row, it can be stored separately from the row. Thus you can specify a DBEFileSet in which to store data for a LONG column.

During an INSERT or UPDATE operation, you specify a LONG column I/O string to indicate where LONG column input data is located and where that data is to be placed when it is later selected or fetched. You indicate either an operating system file or random random heap space.

A LONG column descriptor (rather than the data itself) is selected or fetched into a host variable. Figure 10-1 “ Flow of LONG Column Data and Related Information to the Database” and Figure 10-2 “ Flow of LONG Column Data and Related Information from the Database” illustrate these concepts.

Figure 10-1  Flow of LONG Column Data and Related Information to the Database

Figure 10-2  Flow of LONG Column Data and Related Information from the Database