In this article Barry Mavin, CEO and Chief Software Architect for Recital provides details on how to use the Recital Universal .NET Data Provider with the Recital Database Server.

Overview

A data provider in the .NET Framework serves as a bridge between an application and a data source. A data provider is used to retrieve data from a data source and to reconcile changes to that data back to the data source.

Each .NET Framework data provider has a DataAdapter object: the .NET Framework Data Provider for OLE DB is the OleDbDataAdapter object, the .NET Framework Data Provider for SQL Server is the SqlDataAdapter object, the .NET Framework Data Provider for ODBC is the OdbcDataAdapter object, and the .NET Framework Data Provider for the Recital Database Server is the RecitalDataAdapter object.

The Recital Universal .NET Data Provider can access any data sources supported by the Recital Database Server. It is not restricted to only access Recital data. It can be used to access server-side ODBC, JDBC and OLE DB data sources also.

Core classes of the Data Provider

The Connection, Command, DataReader, and DataAdapter objects represent the core elements of the .NET Framework data provider model. The Recital Universal .NET Data Provider is plug compatible with the .NET Framework Data Provider for SQL Server. All SQL Server classes are prefixed with "Sql" e.g. SqlDataAdaptor. To use the Recital Universal Data Adaptor, simply change the "Sql" prefix to "Recital" e.g. RecitalDataAdaptor.

The following table describes these objects.

Along with the core classes listed in the preceding table, a .NET Framework data provider also contains the classes listed in the following table.

The Recital Universal .NET Data Provider provides connectivity to the Recital Database Server running on any supported platform (Windows, Linux, Unix, OpenVMS) using the RecitalConnection object. The Recital Universal .NET Data Provider supports a connection string format that is similar to the SQL Server connection string format.

The basic format of a connection string consists of a series of keyword/value pairs separated by semicolons. The equal sign (=) connects each keyword and its value.

The following table lists the valid names for keyword values within the ConnectionString property of the RecitalConnection class.

Populating a DataSet from a DataAdaptor

The ADO.NET DataSet is a memory-resident representation of data that provides a consistent relational programming model independent of the data source. The DataSet represents a complete set of data including tables, constraints, and relationships among the tables. Because the DataSet is independent of the data source, a DataSet can include data local to the application, as well as data from multiple data sources. Interaction with existing data sources is controlled through the DataAdapter.

A DataAdapter is used to retrieve data from a data source and populate tables within a DataSet. The DataAdapter also resolves changes made to the DataSet back to the data source. The DataAdapter uses the Connection object of the .NET Framework data provider to connect to a data source and Command objects to retrieve data from and resolve changes to the data source.

The SelectCommand property of the DataAdapter is a Command object that retrieves data from the data source. The InsertCommand, UpdateCommand, and DeleteCommand properties of the DataAdapter are Command objects that manage updates to the data in the data source according to modifications made to the data in the DataSet.

The Fill method of the DataAdapter is used to populate a DataSet with the results of the SelectCommand of the DataAdapter. Fill takes as its arguments a DataSet to be populated, and a DataTable object, or the name of the DataTable to be filled with the rows returned from the SelectCommand.

The Fill method uses the DataReader object implicitly to return the column names and types used to create the tables in the DataSet, as well as the data to populate the rows of the tables in the DataSet. Tables and columns are only created if they do not already exist; otherwise Fill uses the existing DataSet schema.

Examples in C#:

////////////////////////////////////////////////////////////////////////
// include the references below
using System.Data;
using Recital.Data;

////////////////////////////////////////////////////////////////////////
// The following code example creates an instance of a DataAdapter that 
// uses a Connection to the Recital Database Server Southwind database 
// and populates a DataTable in a DataSet with the list of customers. 
// The SQL statement and Connection arguments passed to the DataAdapter 
// constructor are used to create the SelectCommand property of the DataAdapter.
public DataSet SelectCustomers()
{
	RecitalConnection swindConn = new
		RecitalConnection("Data Source=localhost;Initial Catalog=southwind");
	RecitalCommand selectCMD = new
		RecitalCommand("SELECT CustomerID, CompanyName FROM Customers", swindConn);
	selectCMD.CommandTimeout = 30;
	RecitalDataAdapter custDA = new RecitalDataAdapter();
	custDA.SelectCommand = selectCMD;
	swindConn.Open();
	DataSet custDS = new DataSet();
	custDA.Fill(custDS, "Customers");
	swindConn.Close();
	return custDS;
}

////////////////////////////////////////////////////////////////////////
// The following example uses the RecitalCommand, RecitalDataAdapter and 
// RecitalConnection, to select records from a database, and populate a 
// DataSet with the selected rows. The filled DataSet is then returned. 
// To accomplish this, the method is passed an initialized DataSet, a 
// connection string, and a query string that is a SQL SELECT statement
public DataSet SelectRecitalRows(DataSet dataset, string connection, string query) 
{
	RecitalConnection conn = new RecitalConnection(connection);
	SqlDataAdapter adapter = new RecitalDataAdapter();
	adapter.SelectCommand = new RecitalCommand(query, conn);
	adapter.Fill(dataset);
	return dataset;
}

This article discusses the features in Recital that allow data to be imported and exported between platforms in Microsoft® ADO XML Format.

Overview

Extensible Markup Language, XML, is widely regarded as a lingua franca for the interchange of data. XML's text-based, platform-independent format and its integration of data and the schema to define and describe that data, make it the ideal import/export medium. Recital software provides the functionality to output the data from Recital - and other supported table formats such as FoxPro and FoxBASE - into XML file format and to import XML data into those tables' formats. Such import/export operations provide the means to exchange data with third-party applications and can also facilitate the transfer of data between Recital installations on binary-incompatible platforms.

The features examined in this article are available in Recital Terminal Developer and in the Recital Mirage and Recital Database Servers on all Recital supported platforms. Both the Recital/4GL and Recital/SQL provide XML import and export capabilities. The XML files discussed are in Microsoft® ADO XML format.

Microsoft® ActiveX® Data Objects XML Format

The ADO XML format is primarily designed for ADO Recordset persistence and ADO XML files created by Recital can be used in this way and loaded directly into ADO Recordsets. The format can, though also be used for more generic data transfer. An ADO XML file is self-contained, consisting of two sections: a schema section followed by a data section. The schema conforms to the W3C XML-Data specification and defines the data structure.
For additional information on the Microsoft® ActiveX® Data Objects XML Format, please see Appendix 1.

NOTE: The Recital XMLFORMAT setting should always be in its default setting of ADO for ADO XML Format operations.

set xmlformat to ADO

SQL

Recital/SQL offers the ability to export data into XML files using the SELECT and FETCH statements and import from XML using the CREATE TABLE and INSERT statements.

SQL: Exporting

The SELECT...SAVE AS XML statement allows the complete result set from a SELECT statement to be saved as an XML file. This could be a complete table:

open database southwind
  SELECT * from orders SAVE AS XML orders.xml

or a more complex multi-table query:

open database southwind
SELECT orders.orderid, orders.customerid,;
    employees.employeeid, employees.lastname, employees.firstname,;
    orders.orderdate, orders.freight, orders.requireddate,;
    orders.shippeddate, orders.shipvia, orders.shipname,;
    orders.shipaddress, orders.shipcity,;
    orders.shipregion, orders.shippostalcode, orders.shipcountry,;
    customers.companyname, customers.address, customers.city,;
    customers.region, customers.postalcode, customers.country; 
    FROM orders INNER JOIN customers;
    ON customers.customerid = orders.customerid,;
    orders INNER JOIN employees;
    ON orders.employeeid = employees.employeeid;
    SAVE AS XML orderinfo

The resulting XML file can then be further processed within the same or a different Recital environment or transferred to a third party product.

<x-ml xmlns:z="#RowsetSchema" xmlns:rs="urn:schemas-microsoft-com:rowset"
 xmlns:dt="uuid:C2F41010-65B3-11d1-A29F-00AA00C14882" xmlns:s="uuid:BDC6E3F0-6DA3-11d1-A2A3-
00AA00C14882">
 <s:schema id="RowsetSchema">
  <s:elementtype rs:updatable="true" content="eltOnly" name="row">
   <s:attributetype rs:basecolumn="orderid" rs:basetable="orders.dbf" rs:write="true"
 rs:nullable="true" rs:number="1" name="orderid">
   <s:datatype rs:fixedlength="true" rs:precision="14" rs:scale="0" dt:maxlength="10"
 rs:dbtype="numeric" dt:type="number">
   </s:datatype></s:attributetype>
   <s:attributetype rs:basecolumn="customerid" rs:basetable="orders.dbf" rs:write="true"
 rs:nullable="true" rs:number="2" name="customerid">
   <s:datatype rs:fixedlength="true" dt:maxlength="5" rs:dbtype="str" dt:type="string">
   </s:datatype></s:attributetype>
   <s:attributetype rs:basecolumn="employeeid" rs:basetable="orders.dbf" rs:write="true"
 rs:nullable="false" rs:number="3" name="employeeid">
   <s:datatype rs:fixedlength="true" rs:precision="20" rs:scale="0" dt:maxlength="10"
 rs:dbtype="numeric" dt:type="number">
   </s:datatype></s:attributetype>
   <s:attributetype rs:basecolumn="lastname" rs:basetable="orders.dbf" rs:write="true"
 rs:nullable="false" rs:number="4" name="lastname">
   <s:datatype rs:fixedlength="true" dt:maxlength="20" rs:dbtype="str" dt:type="string">
   </s:datatype></s:attributetype>
   <s:attributetype rs:basecolumn="firstname" rs:basetable="orders.dbf" rs:write="true"
 rs:nullable="false" rs:number="5" name="firstname">
   <s:datatype rs:fixedlength="true" dt:maxlength="10" rs:dbtype="str" dt:type="string">
   </s:datatype></s:attributetype>
   <s:attributetype rs:basecolumn="orderdate" rs:basetable="orders.dbf" rs:write="true"
 rs:nullable="true" rs:number="6" name="orderdate">
   <s:datatype rs:fixedlength="true" dt:maxlength="10" rs:dbtype="Date" dt:type="Date">
   </s:datatype></s:attributetype>
   <s:attributetype name="freight" ...

Click image to display full size

Fig 1: Microsoft® Office Excel 2003: orderinfo.xml.

For data accessed through a Recital Database Gateway, such as Oracle, MySQL or PostgreSQL, the FETCH command can be used to save a cursor results set into an XML file:

// Connect to MySQL Database 'mydata' via Recital Database Gateway
nStatHand=SQLSTRINGCONNECT("mys@mysql1:user1/pass1-mydata",.T.)
if nStatHand < 1
  dialog box [Could not connect]
else
  DECLARE cursor1 CURSOR FOR;
      SELECT account_no, last_name, first_name FROM example
  OPEN cursor1
  FETCH cursor1 INTO XML exa1.xml
  SQLDISCONNECT(nStatHand)
endif

SQL: Importing

The CREATE TABLE statement allows a new table to be created based on the structure defined in an XML file. The data from the XML file can optionally be loaded into this new table if the LOAD keyword is included. For example, a new 'orderinfo' table can be created and populated with data from the orderinfo.xml file created by the SELECT...SAVE AS XML statement shown earlier:

open database southwind
SELECT orders.orderid, orders.customerid,;
    employees.employeeid, employees.lastname, employees.firstname,;
    orders.orderdate, orders.freight, orders.requireddate,;
    orders.shippeddate, orders.shipvia, orders.shipname,;
    orders.shipaddress, orders.shipcity,;
    orders.shipregion, orders.shippostalcode, orders.shipcountry,;
    customers.companyname, customers.address, customers.city,;
    customers.region, customers.postalcode, customers.country; 
    FROM orders INNER JOIN customers;
    ON customers.customerid = orders.customerid,;
    orders INNER JOIN employees;
    ON orders.employeeid = employees.employeeid;
    SAVE AS XML orderinfo

CREATE TABLE orderinfo FROM XML orderinfo LOAD

The INSERT statement can be used to load data when the table structure already exists. Taking our earlier orderinfo.xml file again, the data can be loaded using INSERT:

open database southwind;
SELECT orders.orderid, orders.customerid,;
    employees.employeeid, employees.lastname, employees.firstname,;
    orders.orderdate, orders.freight, orders.requireddate,;
    orders.shippeddate, orders.shipvia, orders.shipname,;
    orders.shipaddress, orders.shipcity,;;
    orders.shipregion, orders.shippostalcode, orders.shipcountry,;
    customers.companyname, customers.address, customers.city,;
    customers.region, customers.postalcode, customers.country; 
    FROM orders INNER JOIN customers;
    ON customers.customerid = orders.customerid,;
    orders INNER JOIN employees;
    ON orders.employeeid = employees.employeeid;
    SAVE AS XML orderinfo
CREATE TABLE orderinfo FROM XML orderinfo

INSERT INTO orderinfo FROM XML orderinfo

The examples above show the export and import in a single piece of code. To transfer data between binary-incompatible platforms, the export phase using SELECT...SAVE AS XML would be carried out on the source platform, the resulting XML file would be transferred to the target platform, then the import phase using CREATE TABLE...LOAD or CREATE TABLE + INSERT would be run on the target platform.

Recital/4GL

The Recital/4GL offers the ability to export data into XML files using the COPY TO ... TYPE XML command and import from XML using the XMLFIRST() and XMLNEXT() functions.

Recital/4GL: Exporting

The COPY TO command can be used to export data from Recital and other natively supported tables out to a wide range of formats. This includes exporting to an XML file. The '.xml' file extension is added automatically. The COPY TO command can be used to export an entire table:

open database southwind
use orders
copy to orders type xml

or, using the FIELDS clause and the FOR or WHILE clauses, restrict the field list and export only those records which match a particular condition:

open database southwind
use orders
copy to orders type xml fields orderid for year(orderdate) = 1996

Only the orderid field from those records which match the condition is exported:

<x-ml xmlns:z="#RowsetSchema" xmlns:rs="urn:schemas-microsoft-com:rowset"
 xmlns:dt="uuid:C2F41010-65B3-11d1-A29F-00AA00C14882" xmlns:s="uuid:BDC6E3F0-6DA3-11d1-A2A3-
00AA00C14882">
 <s:schema id="RowsetSchema">
  <s:elementtype rs:updatable="true" content="eltOnly" name="row">
   <s:attributetype rs:basecolumn="ORDERID" rs:basetable="ORDERS" rs:write="true" rs:nullable="true"
 rs:number="1" name="ORDERID">
   <s:datatype rs:fixedlength="true" rs:precision="10" rs:scale="0" dt:maxlength="10"
 rs:dbtype="numeric" dt:type="number">
   </s:datatype></s:attributetype>
  </s:elementtype>
 </s:schema>
 <rs:data>
 <z:row orderid="10248">
 <z:row orderid="10249">
 <z:row orderid="10250">
 <z:row ...

Recital/4GL: Importing

Data from an XML file can be extracted one record at a time using the XMLFIRST() and XMLNEXT() functions. XMLFIRST() reads the first record from an XML file and loads information from the file into a series of memory variables and arrays. The record data is loaded into a one-dimensional array which is created automatically. Each element in the array contains the data for its corresponding field in string format. The field names are loaded into another automatically-created array. The XMLNEXT() function works in a similar way to deal with all the subsequent records in the XML file. The XMLCOUNT() function can be used, as in the example below, to determine how many data records the XML file has.

The Recital/4GL includes a vast range of functions for manipulation and conversion of arrays and their individual elements. In the example program below, the XMLFIRST() and XMLNEXT() functions are used to sequentially extract each record from an XML file, whose name is passed to the program as a parameter. Once loaded into an array, the data is converted to the correct Recital data type then appended into a table. The table name is also passed as a parameter.

procedure replaceit
  append blank
  for i = 1 to numfields
    if type(field(i)) = "N"
      replace &(field(i)) with val(data[&i])
    elseif type(field(i)) = "D"
      replace &(field(i)) with stod(data[&i])
    elseif type(field(i)) = "T"
      replace &(field(i)) with ctot(data[&i])
    elseif type(field(i)) = "L"
      replace &(field(i)) with iif(data[&i]="T",.T.,.F.)
    elseif type(field(i)) = "Y"
      replace &(field(i)) with val(data[&i])
    else
      replace &(field(i)) with data[&i]
    endif
  next
return
 
procedure starthere                    
  parameters cTable, cFile
  numfields=xmlfirst(cFile,targ,trans,where,fldnames,data)
  if numfields < 1
    dialog box [No records in XML file]
  else
    use &cTable
    replaceit()
  endif
  numrecs = xmlcount(cFile)
  if numrecs > 1
    numleft = numrecs -1
    for i = 1 to numleft
      xmlnext(trans,where,fldnames,data)
      replaceit()
    next
  endif
return

Alternative Import/Export Methods

Other features exist in Recital to facilitate the import and export of data:

RDDs

The RDDs, Replaceable Database Drivers, are available on Windows, Linux and all supported 32-bit UNIX platforms. They allow for the use and creation of database tables and indexes in FoxPro, dBase and Clipper formats. The file format is the same across all the platforms that support the RDDs, allowing the tables and indexes to be transferred as required. The formats are also supported by a wide range of third-party products as well as their originating database systems. For more information on the RDDs, please see the online documentation on Xbase migration and the SET FILETYPE command.

BUILD/INSTALL

These are Recital/4GL commands for the export (BUILD) and import (INSTALL) of Recital tables and their associated memo, dictionary and multiple index files in ASCII format to allow them to be transferred across binary incompatible platforms. For more information, please see the online documentation on Recital/4GL commands.

COPY Commands

The COPY TO, COPY STRUCTURE, COPY STRUCTURE EXTENDED and CREATE FROM commands can all be used to enable data to be transferred between different formats and different platforms. For more information, please see the online documentation on Recital/4GL commands.

Appendix 1: Microsoft® ActiveX® Data Objects XML Format

For detailed information on the Microsoft® ActiveX® Data Objects XML Format, please consult the following Microsoft documentation: