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The dbField OMX component allows you to access the data value that exists within a row of a database record set field. This OMX component is a shelf, where each field value is placed in a separate item on the shelf, and each item key is the unique name of the field. Use the dbField OMX component in conjunction with dbDatabase to create a connection to a database and obtain a read-only set of data from that database.
When you use the dbQuery function, the dbField shelf is automatically bound to the record set created by the SQL query that you specify in that function. When you move the data cursor in the record set, using the dbRecordMove function, the dbField shelf is automatically repopulated with whatever values are in the current row. You retrieve values from the dbField OMX variable with the dbFieldValue function.
The OmniMark Database dynamic link library file ("omdb.dll") creates the dbField OMX component. The related include file ("omdb.xin") defines the interface to that component. To use dbField OMX components in your program, you must include the following include statement in your program:
include "omdb.xin"
Within your program, you can create as many instances of the dbField OMX component as you require by declaring global and local shelves of type "dbField". These shelves must be declared as variable. For example:
; required include statement
include "omdb.xin"
; global dbField variable declarations
global dbField my-fields-1 variable
global dbField my-fields-2 variable
process
; local dbField variable declarations
local dbField my-fields-3 variable
local dbField my-fields-4 variable
Once you have declared your dbField OMX shelves, you can use those variables in the dbQuery and dbFieldValue functions that are part of the OmniMark Database library. For example:
include "omdb.xin"
process
local dbDatabase my-database
local dbField my-query variable
local stream SQL-query initial
{ "select C.CourseName, S.StudentName, SC.Grade " ||
"from Student S, Course C, StudentCourse sc " ||
"where SC.CID = C.CID and S.SID = SC.SID " ||
"order by C.CID, SC.Grade desc"
}
set my-database to dbOpenODBC "MyDatabase"
dbQuery my-database sql SQL-query record my-query
repeat
exit unless dbRecordExists my-query
repeat over my-query
output dbFieldValue my-query null '-dnf-'
output '%t' when ! #last
again
output '%n'
dbRecordMove my-query
again
The dbField OMX component is not copyable. This means that when you set the value of one dbField shelf to the value of another dbField shelf, you end up with two variables pointing at the same set of field values. You are able to read from both shelves, but you are actually reading these from the same set of field values, whether you use the original dbField shelf or its copy.
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