HP 3000 Manuals

ALLBASE/SQL Pascal Application Programming Guide

General Concepts 

ALLBASE/SQL stores LONG column data in a database for later retrieval.
LONG column data is not manipulated by ALLBASE/SQL when it is modified or
retrieved.  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 heap space.

A LONG column descriptor (rather than the data itself) is selected or
fetched into a host variable.  Figure 12-1  and Figure 12-2  
illustrate these concepts.


          Figure 12-1.  Flow of LONG Column Data and Related Information to the Database 


          Figure 12-2.  Flow of LONG Column Data and Related Information from the Database 

MPE/iX 5.0 Documentation