Using Catalog Functions
All databases have a structure containing the data stored in the database. A definition of this structure, along with other information such as permissions, is stored in a catalog (implemented as a set of system tables), also known as a data dictionary.
The SQL Native Client ODBC driver enables an application to determine the database structure through calls to ODBC catalog functions. Catalog functions return information in result sets and are implemented using catalog stored procedures to query the system tables in the catalog. For example, an application might request a result set containing information about all the tables on the system or all the columns in a particular table. The standard ODBC catalog functions are used to get catalog information from the SQL Server to which the application connected.
SQL Server supports distributed queries in which data from multiple, heterogeneous OLE DB data sources is accessed in a single query. One of the methods of accessing a remote OLE DB data source is to define the data source as a linked server. This can be done by using sp_addlinkedserver. After the linked server has been defined, objects in that server can be referenced in Transact-SQL statements by using a four-part name:
linked_server_name.catalog.schema.object_name.
The SQL Native Client ODBC driver supports two driver-specific functions that help get catalog information from linked servers:
- SQLLinkedServers
Returns a list of the linked servers defined to the local server. - SQLLinkedCatalogs
Returns a list of the catalogs contained in a linked server.
After you have a linked server name and a catalog name, the SQL Native Client ODBC driver supports getting information from the catalog by using a two-part name of linked_server_name**.**catalog for CatalogName on the following ODBC catalog functions:
- SQLColumnPrivileges
- SQLColumns
- SQLPrimaryKeys
- SQLStatistics
- SQLTablePrivileges
- SQLTables
The two-part linked_server_name**.**catalog is also supported for FKCatalogName and PKCatalogName on SQLForeignKeys.
Using SQLLinkedServers and SQLLinkedCatalogs requires the following files:
- sqlncli.h
Includes function prototypes and constant definitions for the linked server catalog functions. Sqlncli.h must be included in the ODBC application and must be in the include path when the application is compiled. - sqlncli.lib
Must be in the library path of the linker and specified as a file to be linked. Sqlncli.lib is distributed with the SQL Native Client ODBC driver. - sqlncli.dll
Must be present at execution time. Sqlncli.dll is distributed with the SQL Native Client ODBC driver.
См. также
Основные понятия
SQL Native Client (ODBC)
SQLColumnPrivileges
SQLColumns
SQLPrimaryKeys
SQLTablePrivileges
SQLTables
SQLStatistics