| |
RDO Overview
The Remote Data Object Model provides a set of objects that assists in the development of client/server applications by addressing their unique requirements. Unlike DAO which provides an interface to the Jet Database Engine, RDO provides an object-oriented layer of abstraction that directly interfaces with the ODBC API as does the ODBCDirect Interface, RDO uses the ODBC API and the database server driver to create database server connections, create queries and cursors to navigate the resulting data sets, and execute complex stored procedures that rely on the database server for the majority of processing requirements. Unlike DAO, which utilizes the Jet Database Engine for query pre-processing and connection management, RDO directly interfaces to the database server, which makes RDO particularly suited to client/server application development. This section of my site provides a complete reference for the objects provided by RDO and their methods and properties.
rdoColumn
The rdoTable and rdoResultset object's rdoColumn collection, represents the rdoColumn object in a row of data. You can use the rdoColumn object in an rdoResultset to read and set values for the data columns in the current row of the object. However, in most cases, references to the rdoColumn object is only implied because the rdoColumns collection is the rdoResultset object's default collection.
rdoColumn Object Properties
| Property |
Description |
| AllowZeroLength |
Returns a value that indicates whether a zero-length string ("") is a valid setting for the Value property of an rdoColumn object with a data type of rdTypeCHAR, rdTypeVARCHAR, or rdTypeLONGVARCHAR. |
| Attributes |
Returns a value that indicates one or more characteristics of an rdoColumn object. It can be a sum of the following constants: rdFixedColumn — the column size is fixed (default for numeric columns). For example. Char, Binary, rdVariableColumn — the column size is variable. For example, VarChar and LongVarChar, LongBinary and LongVarBinary columns. rdAutoIncrColumn — the column value for the new rows is automatically incremented to a unique value that can't be changed. rdUpdatableColumn — the column value can be changed. rdTimeStampColumn — the column is a timestamp value. This attribute is set only for rdClientBatch cursors. |
| ChunkRequired |
Returns a boolean value that indicates whether data must be accessed using the GetChunk() method. |
| Name |
Returns the name of the RemoteData object. |
| OrdinalPosition |
Returns the relative position of an rdoColumn object within the rdoColumn collection. |
| BatchConflictValue |
Returns a value currently in the database that is newer than the Value property, as determined by an optimistic batch-update conflict. |
| KeyColumn |
Returns or sets a value that specifies whether this column is part of the primary key. |
| Status |
Returns or sets the status of the current row or column. If set to rdRowUnmodified — the row column hasn't been modified of has been updated successfully. If set to rdRowModified — the row column has been modified, but not updated in the database. If set to rdRowNew — the row or column has been inserted with the AddNew() method, but hasn't been inserted yet into the database. If set to rdRowDeleted — the row or column has been deleted, but hasn't been deleted yet into the database. If set to rdRowDBDeleted — the row or column has been deleted locally in the database. |
| Original Value |
Returns the value of the column as the first fetched from the database. |
| Required |
Returns a value that indicates whether an rdoColumn requires a non-Null value. |
| Size |
Returns a value that indicates the maximum size, in bytes, of the underlying data of an rdoColumn object that contains text, or fixed size of an rdoColumn object that contains text or numeric values. |
| SourceColumn |
Returns a value that indicates the name of the column that is the original source of the data for an rdoColumn object. |
| SourceTable |
Returns a value that indicates the name of the table that is the original source of data for an rdoColumn object. |
| Type |
Returns or sets a value that indicates the type or data type of an object. |
| Updatable |
Returns a boolean value that indicates whether changes can be made to a remote data object. |
| Value |
Returns or sets the value of an object. |
rdoColumn Object Methods
| Method |
Description |
| AppendChunk() |
Appends data from a Variant expression to an rdoColumn object with a data type of rdTypeLONGVARBINARY or rdTypeLONGVARCHAR. |
| ColumnSize() |
Returns the number of bytes in an rdoColumn object with a data type of rdTypeLONGVARBINARY or RDTypeLONGVARCHAR. |
| GetChunk() |
Returns all or a portion of the contents of a Memo or Long binary field object in the Fields collection of a Recordset object. |
rdoColumns
The rdoTable, or rdoResultset object's rdoColumns collection, represents the rdoColumn objects in a row of data. You use the rdoColumn object in an rdoResultset to read and set values for the data columns in the current row of the object.
rdoColumns Object Properties
| Property |
Description |
| Item |
Returns a specific member of an RDO collection object, either by position or by key. |
| Count |
Returns the number of objects in a collection. |
The rdoColumns object has one method, Refresh(), whose syntax is Refresh. It has no parameters, and it either closes (and rebuilds the rdoResultset object created by a RemoteData control) or it refreshes the members of the collection in the Applies To list.
Copyright� 2000 by Noel
|