SQL Server 2008 Full-Text Search: Internals and Enhancements
SQL Server Technical Article
Writer: Fernando Azpeitia Lopez, Microsoft Corp.
Published: July 2008
Database systems must go beyond the traditional realm of relational data by covering an increasing amount and variety of unstructured and semistructured information, be it speech, documents, XML, bioinformatics, chemical, or multimedia. Search is a key technology capable of working with vast amounts of data: it is scalable, low-latency, and very user-friendly. It is just what is needed to make a database the best place to store all types of data.
SQL Server 2008 introduces a new Full-Text Engine that is integrated into the relational database. Full-text search is now as fully integrated as any other database service. The main goal for full-text search in SQL Server 2008 was to introduce a new integrated Search platform. In addition to the improvements and gains that come with this integration, this platform provides a strong base for delivering, in the near future, innovative new features and capabilities that combine the strengths of searching and querying.
Full Text Index helps to perform complex queries against character data. These queries can include word or phrase searching. We can create a full-text index on a table or indexed view in a database. Only one full-text index is allowed per table or indexed view. The index can contain up to 1024 columns. Software developer Monica who helped with screenshots also informed that this feature works with RTM (Ready to Manufacture) version of SQL Server 2008 and does not work on CTP (Community Technology Preview) versions.
To create an Index, follow the steps:
Create a Full-Text Catalog
Create a Full-Text Index
Populate the Index
1) Create a Full-Text Catalog
Full – Text can also be created while creating a Full-Text Index in its Wizard.
2) Create a Full-Text Index
3) Populate the Index
As the Index Is created and populated, you can write the query and use in searching records on that table which provides better performance.
We will find the Employee Records who has “Marking “in their Job Title.
FREETEXT( ) Is predicate used to search columns containing character-based data types. It will not match the exact word, but the meaning of the words in the search condition. When FREETEXT is used, the full-text query engine internally performs the following actions on the freetext_string, assigns each term a weight, and then finds the matches.
Separates the string into individual words based on word boundaries (word-breaking).
Generates inflectional forms of the words (stemming).
Identifies a list of expansions or replacements for the terms based on matches in the thesaurus.
CONTAINS( ) is similar to the Freetext but with the difference that it takes one keyword to match with the records, and if we want to combine other words as well in the search then we need to provide the “and” or “or” in search else it will throw an error.
USE AdventureWorks2008 GO
SELECT BusinessEntityID, JobTitle FROM HumanResources.Employee WHERE FREETEXT(*, 'Marketing Assistant');
SELECT BusinessEntityID,JobTitle FROM HumanResources.Employee WHERE CONTAINS(JobTitle, 'Marketing OR Assistant');
SELECT BusinessEntityID,JobTitle FROM HumanResources.Employee WHERE CONTAINS(JobTitle, 'Marketing AND Assistant'); GO
Full text indexing is a great feature that solves a database problem, the searching of textual data columns for specific words and phrases in SQL Server databases. Full Text Index can be used to search words, phrases and multiple forms of word or phrase using FREETEXT() and CANTAINS() with “and” or “or” operators.