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This guide explores Full-Text Searching (FTS) in SQL Server 2012, detailing its installation, components, and functionalities. FTS allows efficient searching on character-based data like text, XML, and more, offering advantages over the LIKE operator. We cover critical aspects like creating FTS indexes, using the CONTAINS and FREETEXT functions, and implementing FILESTREAM and FileTables for managing large objects. With support for over 50 languages and features like stoplists and thesaurus integration, FTS significantly enhances search capabilities in SQL databases.
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Introductionto Full-Text Searching in SQL Server 2012 Adolfo J. Socorro, Ph.D.IT Impact, Inc. asocorro@itimpact.com
Outline • What can we do with FTS? • How to install FTS • FTS components • Creating FTS indexes • How to query with FTS • FILESTREAM and FileTable
FTS Basics FTS allows searching against character-based data • char • varchar • nchar • nvarchar • text • ntext • image • xml • varbinary • varbinary(max)
A First Look • Let’s run some simple examples to get a feel for FTS!
LIKE vs FTS • LIKE works on character patterns only • Cannot use the LIKE predicate to query formatted binary data • FTS is much faster against large amounts of unstructured text data
Supported SQL Server Editions • Enterprise • Business Intelligence • Standard • Web • Express with Advanced Services Available since at least SQL Server 2000
Language Support • 50+ languages • Language-specific components • Word breakers and stemmers • Stoplists • Thesaurus files
FTS Indexes • One index per table or indexed view • Must have a unique, single-column, non-nullable index on the table • Grouped within the same database into one or more full-text catalogs (“containers”)
Full-Text Catalogs • A logical construct • A way to manage FT indexes together
Index Population • Population: the addition of data to full-text indexes
CONTAINS • Precise or prefix matches to single words and phrases • Proximity matches • Logical operations between conditions: AND, OR, AND NOT • Optional use of inflectional formsand thesaurus
FREETEXT • Matching the meaning, but not the exact wording, of specified words or phrases • Always uses inflectional forms and thesaurus
CONTAINSTABLE AND FREETEXTTABLE • Return a relevance ranking value (RANK) and full-text key (KEY) for each row • The actual RANK values are unimportant and typically differ each time the query is run • ISABOUT/WEIGHT influence the rankingin CONTAINSTABLE
Stoplists • A mechanism to discard commonly occurring strings that do not help the search
Thesaurus • Nicknames: Robert/Bob • Common misspellings: calendar/calender • Homophones: Geoff/Jeff • Technical terms: proc/procedure Very powerful if you log searches and learn what users are commonly searching for
Thesaurus • One file per language
Filters • Extract textual information from the document (removing the formatting) • Send the text to the word-breaker component for the language associated with the column • Need to manually install Office 2010 and PDF filters
Why Store in the Database? • Integrating unstructured data into the relational database provides significant benefits: • Integrated storage and data management capabilities (e.g., backup) • Ease of administration and policy management • Full-text search
FILESTREAM • A database/file system hybrid • FILESTREAM is an attribute that can be assigned to a varbinary(max) column • Allows storing BLOB data in the file system • Not restricted to the 2 GB limitSQL Server imposes on BLOBs
FILESTREAM • SQL Server buffer pool is not used • Isolation semantics are governed byDatabase Engine transaction isolation levels
FILESTREAM • All data access must be transactional • Must use specific APIs for file I/O • Do not edit the files directly!
When to Use FILESTREAM • Objects that are being stored are, on average, larger than 1 MB • Store smaller objects in the database • Fast read access is important • You are using a middle tier for application logic
FileTables • A special, fixed-schema kind of table • Builds on top of existing FILESTREAM capabilities • Store files and documents in in the database, but access them from Windows applications as if they were stored in the file system (WIN32 API)
FileTables • Hierarchical namespace • Includes file system properties as columns • Preserves full file names • Non-transactional access through the FS
FileTables • Calls to create or change a file or directory through the Windows share are intercepted by a SQL Server component and reflected in the corresponding relational data in the FileTable
FileTables vs FILESTREAM • File and directory hierarchy maintained in the database • Windows application compatibility • Relational access to file attributes • Both are available in all editions
Wrap Up • Advanced searching on character-based data, including documents • FTS setup, components, and queries • FILESTREAM • FileTables
Other Topics • Document-property search • Semantic search • Optimizations • Query plans and execution traces
References • Posts and presentations by Bob Beauchemin • http://www.sqlskills.com/blogs/bobb/ • Blog: SQL Server FTS Team Blog • http://blogs.msdn.com/b/sqlfts • SQL Server 2012 Books Online • http://msdn.microsoft.com/en-us/library/cc645577(SQL.110).aspx
Filter Packs • Adobe PDF Filter • http://www.adobe.com/support/downloads/thankyou.jsp?ftpID=4025&fileID=3941 • Office 2010 Filters • http://www.microsoft.com/en-us/download/details.aspx?id=17062