SQL Server: how to optimize “like” queries?

Question

I have a query that searches for clients using \"like\" with wildcard. For example:

SELECT TOP (10) 
       [t0].[CLIENTNUMBER], 
       [t0].[FIRSTNAME], 
          


        

Answer 1

To do much for a LIKE where the pattern has the form '%XXX%', you want to look up SQL Server's full-text indexing capability, and use CONTAINS instead of LIKE. As-is, you're doing a full table scan, because a normal index won't help with a search for an item that starts with a wild card -- but a full-text index will.

/* ... */
 WHERE (LTRIM(RTRIM([t0].[DOCREVNO])) = '0') 
   AND (contains([t0].[FIRSTNAME], 'John')) 
   AND (contains([t0].[LASTNAME], 'Smith')) 
   AND (contains([t0].[SSN], '123'))
   AND (contains([t0].[CLIENTNUMBER],'123')) 
   AND (contains([t0].[MDOCNUMBER], '123')) 
   AND ([t0].[CLIENTINDICATOR] = 'ON')

Answer 2

Looks like some databases (PostgreSQL 7.1+, MySQL v3.23.23+, Microsoft-SQL v???, ) already contains such things:

MySQL>> ALTER TABLE articles ADD FULLTEXT(body, title); MySQL>> SELECT * FROM articles WHERE MATCH(title, body) AGAINST ('PHP') MS-SQL>> SELECT ProductName FROM Products WHERE FREETEXT (ProductName, 'spread' ) PgSQL>> CREATE FUNCTION fti() RETURNS opaque AS '/path/to/fti.so' LANGUAGE 'C'; PgSQL>> CREATE TABLE articles_fti (string type, id oid); .... Oracle..., Sybase...