Cómo hacer consultas distribuidas de SQL Server 2000 con archivos .dbf de FoxPro


Resumen


En este artículo se demuestra cómo realizar una consulta distribuida de SQL Server para recuperar los datos de los archivos .dbc y.dbf de FoxPro utilizando el Controlador ODBC de VFP o el Proveedor OLE DB de VFP.

Más información


Microsoft SQL Server 2000 permite realizar consultas con los proveedores OLE DB. Para ello, se usan las funciones OpenQuery u OpenRowset de Transact-SQL, o una consulta con nombres de cuatro partes que incluya un nombre de servidor vinculado.

Por ejemplo:

sp_addlinkedserver 'mylinkedserver', 'product_name', 'myoledbprovider', 'data_source','location', 'provider_string', 'catalog'

SELECT * FROM OPENQUERY(mylinkedserver, 'select * from table1')

Debería utilizar el Proveedor de Microsoft OLE DB para ODBC (MSDASQL) y el controlador ODBC de Visual FoxPro para configurar un servidor vinculado con el fin de realizar consultas distribuidas con los archivos .dbc y .dbf de FoxPro. No se admite el uso del Proveedor OLEDB de Jet con FoxPro. El Controlador ODBC de Visual FoxPro no es seguro para usar subprocesos. Dado que SQL Server es multiproceso, el Controlador ODBC de Visual FoxPro puede provocar problemas en algunas circunstancias. Si es posible, recomendamos utilizar el Proveedor OLE DB de Visual FoxPro para conectar con los datos de SQL Server.

El ejemplo de código de T-SQL siguiente demuestra cómo configurar y utilizar consultas distribuidas con FoxPro y las funciones OpenQuery y OpenRowset. También demuestra cómo actualizar una tabla de FoxPro remota desde SQL Server 2000. Puede probar este código en el Analizador de consultas SQL después de instalar el Controlador ODBC de Visual FoxPro en un equipo de SQL Server 2000. Tendrá que cambiar los nombres de los orígenes de datos y la ruta de acceso de los archivos de FoxPro según corresponda:
/* OPENROWSET and OPENQUERY examples with VFP via ODBC OLE DB provider */ 

/* These OPENROWSET examples depend on the sample files VFP98\data\Testdata.dbc
Modify your code accordingly for differences in location or DBC name */

--====================================================
-- Using DBC file , read and update
--====================================================
-- OPENROWSET DSN-less example

select * from openrowset('MSDASQL',
'Driver=Microsoft Visual FoxPro Driver;
SourceDB=e:\VFP98\data\Testdata.dbc;
SourceType=DBC',
'select * from customer where country != "USA" order by country')
go

select * from openrowset('MSDASQL',
'Driver=Microsoft Visual FoxPro Driver;
SourceDB=e:\VFP98\data\Testdata.dbc;
SourceType=DBC',
'select * from customer where region="WA"')
go

Update openrowset('MSDASQL',
'Driver=Microsoft Visual FoxPro Driver;
SourceDB=e:\VFP98\data\Testdata.dbc;
SourceType=DBC',
'select * from customer where region="WA"')
set region = "Seattle"
go

-- check to verify which rows were updated
select * from openrowset('MSDASQL',
'Driver=Microsoft Visual FoxPro Driver;
SourceDB=e:\VFP98\data\Testdata.dbc;
SourceType=DBC',
'select * from customer where region="Seattle"')
go

-- OPENROWSET DSN example
/* Note the DSN Example might fail if SQL Server is configured to use a local account.*/
select * from openrowset('MSDASQL',
'DSN=Visual FoxPro Database;
SourceDB=e:\VFP98\data\Testdata.dbc;
SourceType=DBC',
'select * from customer where country != "USA" order by country'
go

/* sp_addlinkedserver examples */
-- sp_addlinkedserver example with DSN

/* You will need to make a DSN and point it to the Testdata database.
Modify your code accordingly for differences in location or DBC name */

/* Note this Example may fail if SQL Server is configured to use a local account.*/
sp_addlinkedserver 'VFP Testdata Database With DSN',
'',
'MSDASQL',
'VFP System DSN'
go

sp_addlinkedsrvlogin 'VFP Testdata Database With DSN', FALSE, NULL, NULL, NULL
go

SELECT *
FROM OPENQUERY([VFP Testdata Database With DSN], 'select * from customer where region = "Seattle" ')
go

-- Update using OpenQuery
Update OPENQUERY([VFP Testdata Database With DSN], 'select * from customer where region="WA"')
set region = "Seattle"
go

/* SP_addlinkedserver example with DSN-less connection */

/* This example also depends on the sample files Testdata.dbc
Modify your code accordingly for differences in location or DBC name */

sp_addlinkedserver 'VFP Testdata Database With No DSN',
'',
'MSDASQL',
NULL,
NULL,
'Driver={Microsoft Visual FoxPro Driver};UID=;PWD=;SourceDB=e:\VFP98\data\Testdata.dbc;SourceType=DBC;Exclusive=No;BackgroundFetch=Yes;Collate=Machine;'
go

sp_addlinkedsrvlogin 'VFP Testdata Database With No DSN', FALSE, NULL, NULL, NULL
go

SELECT *
FROM OPENQUERY([VFP Testdata Database With No DSN], 'select * from customer where country != "USA" order by country')
go

--====================================================
-- Using VFP 6.0 driver, read and update data from VFP sample dbf files
--====================================================

-- OPENROWSET DSN-less example

select * from openrowset('MSDASQL',
'Driver=Microsoft Visual FoxPro Driver;
SourceDB=e:\VFP98\data;
SourceType=DBF',
'select * from customer where country != "USA" order by country')
go

-- perform UPDATE

Update openrowset('MSDASQL',
'Driver=Microsoft Visual FoxPro Driver;
SourceDB=e:\VFP98\data;
SourceType=DBF',
'select * from customer where region="Seattle"')
set region = "WA"
go

-- verify update

select * from openrowset('MSDASQL',
'Driver=Microsoft Visual FoxPro Driver;
SourceDB=e:\VFP98\data;
SourceType=DBF',
'select * from customer where region = "WA"')
go

-- OPENROWSET DSN example
-- DSN points to the folder where .dbf files are.
/* Note this Example may fail if SQL Server is configured to use a local account.*/
select * from openrowset('MSDASQL',
'DSN=Visual FoxPro Tables;
SourceDB=e:\VFP98\data;
SourceType=DBF',
'select * from customer where country != "USA" order by country')
go"?
-- SQL Server's QUOTED_IDENTIFIER has to be set to OFF.



SET QUOTED_IDENTIFIER OFF



-- OPENROWSET DSN-less example



select * from openrowset('MSDASQL',

'Driver=Microsoft Visual FoxPro Driver;

SourceDB=e:\VFP90\samples\data\Testdata.dbc;

SourceType=DBC',

'select * from customer where country = "USA" order by city')

go



select * from openrowset('MSDASQL',

'Driver=Microsoft Visual FoxPro Driver;

SourceDB=e:\VFP90\samples\data\Testdata.dbc;

SourceType=DBC',

'select * from customer where region="WA"')

go



Update openrowset('MSDASQL',

'Driver=Microsoft Visual FoxPro Driver;

SourceDB=e:\VFP90\samples\data\Testdata.dbc;

SourceType=DBC',

'select * from customer where city = "Seattle"')

set region = "WW"

go



-- check to verify which rows were updated

select * from openrowset('MSDASQL',

'Driver=Microsoft Visual FoxPro Driver;

SourceDB=e:\VFP90\samples\data\Testdata.dbc;

SourceType=DBC',

'select * from customer where region="WW"')

go



-- OPENROWSET DSN example

/* Note the DSN Example might fail if SQL Server is configured to use a local account.*/

select * from openrowset('MSDASQL',

'DSN=Visual FoxPro Database;

SourceDB=e:\VFP90\samples\data\Testdata.dbc;

SourceType=DBC',

'select * from customer where country = "USA" order by city')

go



/* sp_addlinkedserver examples */

-- sp_addlinkedserver example with DSN



/* You will need to make a DSN and point it to the Testdata database.

Modify your code accordingly for differences in location or DBC name */



/* Note this Example may fail if SQL Server is configured to use a local account.*/

sp_addlinkedserver 'VFP Testdata Database With DSN',

'',

'MSDASQL',

'VFP System DSN'

go



sp_addlinkedsrvlogin 'VFP Testdata Database With DSN', FALSE, NULL, NULL, NULL

go



SELECT *

FROM OPENQUERY([VFP Testdata Database With DSN], 'select * from customer where city = "Seattle" ')

go



-- We will set the region back to "WA" if it currently is "WW".

-- Update using OpenQuery

Update OPENQUERY([VFP Testdata Database With DSN], 'select * from customer where city = "Seattle" ')

set region = "WA"

go



-- Make sure that the region got updated.

SELECT *

FROM OPENQUERY([VFP Testdata Database With DSN], 'select * from customer where city = "Seattle" ')

go



/* SP_addlinkedserver example with DSN-less connection */



/* This example also depends on the sample files Testdata.dbc

Modify your code accordingly for differences in location or DBC name */



sp_addlinkedserver 'VFP Testdata Database With No DSN',

'',

'MSDASQL',

NULL,

NULL,

'Driver={Microsoft Visual FoxPro Driver};UID=;PWD=;SourceDB=e:\VFP90\samples\data\Testdata.dbc;SourceType=DBC;Exclusive=No;BackgroundFetch=Yes;Collate=Machine;'

go



sp_addlinkedsrvlogin 'VFP Testdata Database With No DSN', FALSE, NULL, NULL, NULL

go



SELECT *

FROM OPENQUERY([VFP Testdata Database With No DSN], 'select * from customer where country = "USA" order by city')

go



--====================================================

-- Using VFP 6.0 driver, read and update data from VFP sample dbf files

--====================================================



-- OPENROWSET DSN-less example



select * from openrowset('MSDASQL',

'Driver=Microsoft Visual FoxPro Driver;

SourceDB=e:\VFP90\samples\data;

SourceType=DBF',

'select * from customer where country != "USA" order by country')

go



-- perform UPDATE



Update openrowset('MSDASQL',

'Driver=Microsoft Visual FoxPro Driver;

SourceDB=e:\VFP90\samples\data;

SourceType=DBF',

'select * from customer where city = "Seattle"')

set region = "WW"

go



-- verify update



select * from openrowset('MSDASQL',

'Driver=Microsoft Visual FoxPro Driver;

SourceDB=e:\VFP90\samples\data;

SourceType=DBF',

'select * from customer where region = "WW"')

go



-- OPENROWSET DSN example

-- DSN points to the folder where .dbf files are.

/* Note this Example may fail if SQL Server is configured to use a local account.*/

select * from openrowset('MSDASQL',

'DSN=Visual FoxPro Tables;

SourceDB=e:\VFP90\samples\data;

SourceType=DBF',

'select * from customer where country != "USA" order by country')

go

También puede utilizar el Proveedor OLE DB de Visual FoxPro para crear una consulta distribuida. Ésta es la mejor tecnología que se puede usar. Tenga en cuenta que aunque este código demuestra cómo actualizar y eliminar los datos, la adición, actualización (modificación) y eliminación de los datos no se admite en una consulta distribuida que use el Proveedor OLE DB.

El ejemplo de código de T-SQL siguiente demuestra cómo configurar y utilizar consultas distribuidas con FoxPro y las funciones OpenQuery y OpenRowset. Puede probar este código en el Analizador de consultas SQL después de instalar el Proveedor OLE DB de Visual FoxPro en un equipo de SQL Server 2000. Tendrá que cambiar los nombres de los orígenes de datos y la ruta de acceso de los archivos de FoxPro según corresponda:
 '/* These OPENROWSET examples depend on the sample files VFP98\data\Testdata.dbc

'Modify your code accordingly for differences in location or DBC name */



--*====================================================

--* Using the DBC file, reading and updating data.

--*====================================================

--* A couple of OPENROWSET queries.

select * from openrowset('VFPOLEDB',

'e:\vfp7junk\Testdata.dbc';'Exclusive=No';'Data Source=DBC',

'select * from customer where country != "USA" order by country')

go



Select * from openrowset('VFPOLEDB',

'e:\vfp7junk\Testdata.dbc';'Exclusive=No';'Data Source=DBC',

'select * from customer where region="WA"')

go



--* Need to use an error trapping routine with the UPDATE and DELETE functions:

select * from

openrowset('VFPOLEDB',

'E:\VFP7Junk\Testdata.DBC';'Exclusive=No';'Data Source=DBC',

'Update Customer Set city = "SEATTLE" where region = "WA" ')

go

declare @upderror int

select @upderror = @@error

print ''

if @upderror != 7357 and @upderror != 0

print 'Update failed with error '+convert(varchar(5),@upderror)

else

print 'Ignore the error above, the Update succeeded'

go





-- check to verify which rows were updated

select * from openrowset('VFPOLEDB',

'E:\VFP7junk\Testdata.DBC';'Exclusive=No';'Data Source=DBC',

'select * from customer where region = "WA"')

go



--* Change the City field back to "Seattle".



select * from

openrowset('VFPOLEDB',

'E:\VFP7Junk\Testdata.DBC';'Exclusive=No';'Data Source=DBC',

'Update Customer Set city = "Seattle" where region = "WA" ')

go

declare @upderror int

select @upderror = @@error

print ''

if @upderror != 7357 and @upderror != 0

print 'Update failed with error '+convert(varchar(5),@upderror)

else

print 'Ignore the error above, the Update succeeded'

go



--* The DELETE fucntion also causes an error, but the DELETE works.

select * from

openrowset('VFPOLEDB',

'E:\VFP7Junk\Testdata.DBC';'Exclusive=No';'Data Source=DBC',

'Delete from Customer where country = "Spain" ')

go

declare @delerror int

select @delerror = @@error

print ''

if @delerror != 7357 and @delerror != 0

print 'Delete failed with error '+convert(varchar(5),@delerror)

else

print 'Ignore the error above, the Delete succeeded'

go



--* Check to see that the records are deleted.

Select * from openrowset('VFPOLEDB',

'e:\vfp7junk\Testdata.dbc';'Exclusive=No';'Data Source=DBC',

'select * from customer where country = "Spain"')

go





--* Here are some examples using the VFP OLE DB Provider to create Linked Servers.

--* Using sp_addlinkedserver to create the Linked Server.

sp_addlinkedserver @server='VFP_Linked_Server',

@srvproduct='Microsoft Visual FoxPro OLE DB Provider',

@provider='VFPOLEDB',

@datasrc = 'E:\vfp7junk'

go



SELECT *

FROM OPENQUERY([VFP_Linked_Server], 'select * from customer where city = "Seattle"')

go





-- The Update command will update the table with the OPENQUERY function when using the

-- linked server, but the same error 7357 error will occur.

select * from

OPENQUERY([VFP_Linked_Server],

'Update Customer Set city = "SEATTLE" where region = "WA" ')

go

declare @upderror int

select @upderror = @@error

print ''

if @upderror != 7357 and @upderror != 0

print 'Update failed with error '+convert(varchar(5),@upderror)

else

print 'Ignore the error above, the Update succeeded'

go





-- Check and see if the City field is all uppercase with "SEATTLE".

SELECT *

FROM OPENQUERY([VFP_Linked_Server], 'select * from customer where region = "WA"')

go



--* Let's check for how many records have the word "London" in the City field.

SELECT *

FROM OPENQUERY([VFP_Linked_Server], 'select * from customer where city = "London"')

go



-- We can also use the Delete command to remove records with the OPENQUERY function when using the

-- linked server, but the same error 7357 error will occur.

select * from

OPENQUERY([VFP_Linked_Server],

'Delete from Customer where city = "London"')

go

declare @delerror int

select @delerror = @@error

print ''

if @delerror != 7357 and @delerror != 0

print 'Delete failed with error '+convert(varchar(5),@delerror)

else

print 'Ignore the error above, the Delete succeeded'

go





/* SP_addlinkedserver example with DSN-less connection */



/* This example also depends on the sample files Testdata.dbc

Modify your code accordingly for differences in location or DBC name */



sp_addlinkedserver 'VFP Testdata Database With No DSN',

'',

'MSDASQL',

NULL,

NULL,

'Driver={Microsoft Visual FoxPro Driver};UID=;PWD=;SourceDB=e:\VFP8junk\Testdata.dbc;SourceType=DBC;Exclusive=No;BackgroundFetch=Yes;Collate=Machine;'

go





SELECT *

FROM OPENQUERY([VFP Testdata Database With No DSN], 'select * from customer where country = "USA" order by country')

go

Referencias


Para obtener más información acerca de cómo configurar y usar consultas distribuidas, consulte sp_addlinkedserver, OpenQuery, OpenRowset y otros temas relacionados en los Libros en pantalla de SQL Server 7.0.

Para obtener más información sobre los archivos .dbf y .dbc de FoxPro, consulte la documentación de producto de FoxPro.