Sql Server Search Full Text Search

Implementing Full Text Search in SQL Server: A Comprehensive Guide

When developing applications that interact with database systems, one challenge that often arises is the ability to perform effective searches across multiple fields. This is especially relevant when searching for people’s names, where users expect to find results based on partial queries and variations. In this post, we will tackle a common issue faced by developers working with SQL Server: implementing an efficient full text search for names across various columns.

The Problem

The developer faced an issue where searching for names using the SQL Server Full Text Search produced inconsistent results. The scenario involved a table with three columns dedicated to names: First Name, Middle Name, and Last Name. Users could input either a full name or parts of the name, but only certain queries returned results. For example:

  • A search for Fry returned the expected result for “Phillip Fry.”
  • However, when searching for Phillip Fry, Fr, or Phil, no results appeared.
  • Inconsistent behavior was also noted for other names, such as Wong.

This inconsistency arose from how the search queries were constructed. The initial implementation using the CONTAINSTABLE function lacked the flexibility needed for partial word searches.

The Solution

The good news is that with some modifications to the query, the full text search can work correctly and provide the desired results even with partial inputs. Here’s how to make adjustments to the SQL query:

Step 1: Modify the Search String

The key modification is how the search string is constructed. Instead of relying solely on direct input, we can utilize wildcard characters (*) and split the input upon spaces to create a more flexible search pattern.

Example Implementation

Here’s the altered version of the SQL query:

@Name nvarchar(100),
...
-- Added this line to format the search string correctly
DECLARE @SearchString varchar(100)

-- Replace spaces with wildcard patterns
SET @SearchString = REPLACE(@Name, ' ', '*" OR "*')
SET @SearchString = '"*'+@SearchString+'*"'

SELECT Per.Lastname, Per.Firstname, Per.MiddleName
FROM Person as Per
INNER JOIN CONTAINSTABLE(Person, (LastName, Firstname, MiddleName), @SearchString) AS KEYTBL
ON Per.Person_ID = KEYTBL.[KEY]
WHERE KEY_TBL.RANK > 2
ORDER BY KEYTBL.RANK DESC;

Explanation of Changes

  1. Wildcard Addition: By adding * before and after the search terms, we allow SQL Server to capture partial matches. This means that if a user searches for Phillip, it will find names that include Phillip.

  2. Space Handling: The REPLACE function transforms input like Amy Wong into a format SQL Server can interpret as separate terms. It replaces spaces with the search syntax required to find variations.

  3. Rank Filtering: The query also ensures that only results with a certain RANK are displayed, helping to prioritize the most relevant matches.

Conclusion

By enhancing your SQL Server queries with these techniques, you will improve the efficiency and accuracy of your full text search functionality. This not only enhances user experience but also makes the application feel more responsive to entry variations. Always remember that the key to effective searching often rests in how the input is understood and processed by the database.

By implementing these strategies, your application will provide effective search results, assisting users in finding the information they need, regardless of how they enter their search queries. If you have any further questions or need additional clarification, feel free to reach out!