The full-text query support introduced in Microsoft® SQL Server™ version 7.0 supports sophisticated searches on character string columns.
This capability is implemented by the Microsoft Search service, which has two roles:
Implements the full-text catalogs and indexes defined for a database. Accepts definitions of full-text catalogs, and the tables and columns making up the indexes in each catalog. Implements requests to populate the full-text indexes.
Processes full-text search queries. Determines which entries in the index meet the full-text selection criteria. For each entry that meet the selection criteria, it returns the identity of the row plus a ranking value to the MSSQLServer service, where this information is used to construct the query result set. The types of queries supported include searching for:
The full-text engine runs as a service named Microsoft Search on Microsoft Windows NT® Server. It is installed when the Full-Text Search feature is selected during custom installation. The Microsoft Search service itself is not installed during a Desktop SQL Server installation. While this means that the Microsoft Search service is not installed on either Microsoft Windows® 95/98 or Windows NT Workstation clients, these clients can make use of the service when connected to a SQL Server Standard or Enterprise installation.
The full-text catalogs and indexes are not stored in a SQL Server database. They are stored in separate files managed by the Microsoft Search service. The full-text catalog files are not recovered during a SQL Server recovery. They also cannot be backed up and restored using the Transact-SQL BACKUP and RESTORE statements. The full-text catalogs must be resynchronized separately after a recovery or restore operation. The full-text catalog files are accessible only to the Microsoft Search service and the Windows NT system administrator.
Communications between SQL Server and the Microsoft Search service are made through a full-text provider.
The full-text catalogs, indexes, and searches supported by the Microsoft Search service apply only to tables in SQL Server databases. The Windows NT Indexing Service provides similar functionality against operating system files. Indexing Service includes an OLE DB Provider for Indexing Service for OLE DB consumers. SQL Server applications can access the OLE DB Provider for Indexing Service through distributed queries. Transact-SQL statements can combine full-text searches referencing SQL Server tables with textual searches of file data by using both the full-text SQL constructs with distributed query references to the OLE DB Provider for Indexing Service. For more information, see Full-text Querying of File Data.
| Microsoft Search Service | Full-text Catalogs and Indexes |
| Full-text Querying SQL Server Data | Full-text Indexes |