How hard is it to incorporate full text search with SQL Server?

Question

I am building a C#/ASP.NET app with an SQL backend. I am on deadline and finishing up my pages, out of left field one of my designers incorporated a full text search on one

Answer 1

I've been there. It works like a charm until you start to consider scalability and advanced search functionalities like search over multiple columns with giving each one different weight values.

For example, the only way to search over Title and Summary columns is to have a computed column with SearchColumn = CONCAT(Title, Summary) and index over SearchColumn. Weighting? SearchColumn = CONCAT(CONCAT(Title,Title), Summary) something like that. ;) Filtering? Forget about it.

Answer 2

"How hard is it" is a tough question to answer. For example, someone who's already done it 10 times will probably reckon it's a snap. All I can really say is that you're likely to find it a lot easier if you use something like NLucene rather than rolling your own.

Answer 3

I have used dtSearch before for adding full text searching to files and databases, and their stuff is pretty cheap and easy to use.

Short of adding all that and configuring SQL, This script will search through all columns in a database and tell you what columns contain the values you are looking for. I know its not the "proper" solution, but may buy you some time.

/*This script will find any text value in the database*/
/*Output will be directed to the Messages window. Don't forget to look there!!!*/

SET NOCOUNT ON
DECLARE @valuetosearchfor varchar(128), @objectOwner varchar(64)
SET @valuetosearchfor = '%staff%' --should be formatted as a like search 
SET @objectOwner = 'dbo'

DECLARE @potentialcolumns TABLE (id int IDENTITY, sql varchar(4000))

INSERT INTO @potentialcolumns (sql)
SELECT 
    ('if exists (select 1 from [' +
    [tabs].[table_schema] + '].[' +
    [tabs].[table_name] + 
    '] (NOLOCK) where [' + 
    [cols].[column_name] + 
    '] like ''' + @valuetosearchfor + ''' ) print ''SELECT * FROM [' +
    [tabs].[table_schema] + '].[' +
    [tabs].[table_name] + 
    '] (NOLOCK) WHERE [' + 
    [cols].[column_name] + 
    '] LIKE ''''' + @valuetosearchfor + '''''' +
    '''') as 'sql'
FROM information_schema.columns cols
    INNER JOIN information_schema.tables tabs
        ON cols.TABLE_CATALOG = tabs.TABLE_CATALOG
            AND cols.TABLE_SCHEMA = tabs.TABLE_SCHEMA
            AND cols.TABLE_NAME = tabs.TABLE_NAME
WHERE cols.data_type IN ('char', 'varchar', 'nvchar', 'nvarchar','text','ntext')
    AND tabs.table_schema = @objectOwner
    AND tabs.TABLE_TYPE = 'BASE TABLE'
ORDER BY tabs.table_catalog, tabs.table_name, cols.ordinal_position

DECLARE @count int
SET @count = (SELECT MAX(id) FROM @potentialcolumns)
PRINT 'Found ' + CAST(@count as varchar) + ' potential columns.'
PRINT 'Beginning scan...'
PRINT ''
PRINT 'These columns contain the values being searched for...'
PRINT ''
DECLARE @iterator int, @sql varchar(4000)
SET @iterator = 1
WHILE @iterator <= (SELECT Max(id) FROM @potentialcolumns)
BEGIN
    SET @sql = (SELECT [sql] FROM @potentialcolumns where [id] = @iterator)
    IF (@sql IS NOT NULL) and (RTRIM(LTRIM(@sql)) <> '')
    BEGIN
        --SELECT @sql --use when checking sql output
        EXEC (@sql)
    END
    SET @iterator = @iterator + 1
END

PRINT ''
PRINT 'Scan completed'

Answer 4

First off, you need to enabled Full text Searching indexing on the production servers, so if thats not in scope, your not going to want to go with this.

However, if that's already ready to go, full text searching is relatively simple.

T-SQL has 4 predicates used for full text search:

• FREETEXT
• FREETEXTTABLE
• CONTAINS
• CONTAINSTABLE

FREETEXT is the simplest, and can be done like this:

SELECT UserName
FROM Tbl_Users
WHERE FREETEXT (UserName, 'bob' )

Results:

JimBob
Little Bobby Tables

FREETEXTTABLE works the same as FreeTEXT, except it returns the results as a table.

The real power of T-SQL's full text search comes from the CONTAINS (and CONTAINSTABLE) predicate...This one is huge, so I'll just paste its usage in:

CONTAINS
    ( { column | * } , '< contains_search_condition >' 
    ) 

< contains_search_condition > ::= 
        { < simple_term > 
        | < prefix_term > 
        | < generation_term > 
        | < proximity_term > 
        | < weighted_term > 
        } 
        | { ( < contains_search_condition > ) 
        { AND | AND NOT | OR } < contains_search_condition > [ ...n ] 
        } 

< simple_term > ::= 
    word | " phrase "

< prefix term > ::= 
    { "word * " | "phrase * " }

< generation_term > ::= 
    FORMSOF ( INFLECTIONAL , < simple_term > [ ,...n ] ) 

< proximity_term > ::= 
    { < simple_term > | < prefix_term > } 
    { { NEAR | ~ } { < simple_term > | < prefix_term > } } [ ...n ] 

< weighted_term > ::= 
    ISABOUT 
        ( { { 
                < simple_term > 
                | < prefix_term > 
                | < generation_term > 
                | < proximity_term > 
                } 
            [ WEIGHT ( weight_value ) ] 
            } [ ,...n ] 
        ) 

This means you can write queries such as:

SELECT UserName
FROM Tbl_Users
WHERE CONTAINS(UserName, '"little*" NEAR tables')

Results:

Little Bobby Tables

Good luck :)

Answer 5

Full text search in SQL Server is really easy, a bit of configuration and a slight tweak on the queryside and you are good to go! I have done it for clients in under 20 minutes before, being familiar with the process

Here is the 2008 MSDN article, links go out to the 2005 versions from there