Omron CX-Supervisor, Руководство пользователя

Страница: 191 / 334

Configuring Parameter Associations SECTION 12 Databases
190
12-4-4-1 Access field by index
When checked, a numeric index is used to identify a particular field instead of
its name. This is useful if you want to configure generic field associations.
Automatically read on open
When checked, the data is transferred from the Recordset field to the
associated point, when the Recordset is opened.
12-4-4-2 Field Paging
You can work with a single record at a time by associating points with the
required fields, and process the data one record at a time. However, if the
point specified is an Array point the whole array will be processed i.e. multiple
fields will be read, written or added. This concept is called Paging. Paging is
supported by the Database script functions, enabling you to manipulate and
navigate the database a page at a time. CX-Supervisor determines the page
size, by using the number of elements in the Array point used in Field
Associations, i.e. if an array point with 10 elements is used then a page size of
10 will be used. In order for paging to work sensibly, you should ensure that all
array points used in multiple field associations for a particular Recordset are of
the same size. If arrays, of differing length are used, the smallest array size
will be adopted as the page size.
12-5 Configuring Parameter Associations
When a Recordset which is defined as a Server Query is opened, the query is
executed, and the set of records produced. The Server Query may be defined
in the database as requiring parameters to be passed which allow criteria to be
passed to the query. Recordsets defined in CX-Supervisor as Server Queries
may have Parameter Associations added to the recordset. Recordsets defined
as a Table Name or SQL Text do not use parameters, hence any Parameter
Associations are ignored.
Size the maximum width of the field
Add used to add new fields to a record
Note: The Name, Type and Size properties are fixed for all entries of the column,
whereas the field value depends on the current position of the Recordset.
Note: The 'Add' property is specifically designed to enable fields to be added
together to create new records. They are not involved in any read operations,
as with the other field property types. For this reason, the 'Automatically read
on open' checkbox is disabled when this type is applied. When creating
configurations to add new records you will need to create a 'Add' association
for every field required to 'create' a valid record i.e. primary keys, non-null
values etc. need to be catered for. See DBAddNew() for more details.
Note: Paging only operates on Field Associations that have the Property Type 'Value'
selected, this enables you to have Field Associations with a Property Type of
'Name' or 'Add' associated with single points in the same Recordset, without
effecting the page size determined by the array points.
Note: Paging is designed to operate at the Recordset level (the concept of levels is
explained in the chapter on DB Script functions). If you perform a Read
operation on a recordset that has paging in force, then a 'page' of records will
be read into all the Field Associations connected to the Recordset. In contrast
to performing a read operation at the Field level which will override the page
size and use the individual fields length.