Can CONTAINS Handle Table Columns that have NULL values? - sql

Question

I'm trying to do some query performance and I've been looking into applying a FULLTEXT INDEX as compared to using LIKE.
I have a database w/person information, i.e. FirstName, LastName, etc. where some of those columns are null.
When I try to use CONTAINS object, I'm getting this error message;
Null or empty full-text predicate
I've put in code to ensure the passed in #FirstName field is not null, and if a null was passed in then I've set it to ' "" ' like I've read elsewhere. I still get the error message. I'm starting to wonder if it's a problem because the index has columns that are null.
Does anyone know if that is the case, I've looked everywhere and I cannot find any information on this.
Here is the query. The #FirstNameLocal and #LastNameLocal are passed into this stored procedure. In this example, FirstName and/or LastName field data in the PersonTable could be null. I'm using SQL Server 2012 w/SP1. "Try to use" means when I try to run the query in SQL Management Studio.
SELECT DISTINCT LastName, FirstName, MiddleName, PersonId
FROM PersonTable
Where IsDeleted = 0
AND CONTAINS(FirstName, #FirstNameLocal)
AND CONTAINS(LastName, #LastNameLocal)

Answer 1

You could check whether your variable IS NULL or equals an empty string first. I think though that this will partially negate the benefit of full-text indexes and you should consider handling this differently (for instance with dynamic SQL).
SELECT DISTINCT LastName, FirstName, MiddleName, PersonId
FROM PersonTable
Where IsDeleted = 0
AND (ISNULL(#FirstNameLocal,'')='' OR CONTAINS(FirstName, #FirstNameLocal))
AND (ISNULL(#LastNameLocal,'')='' OR CONTAINS(LastName, #LastNameLocal));
If you would do this with dynamic SQL it would look something like this:
DECLARE #stmt NVARCHAR(4000);
SET #stmt=
N'SELECT DISTINCT LastName, FirstName, MiddleName, PersonId ' +
N'FROM PersonTable ' +
N'Where IsDeleted = 0' +
CASE WHEN ISNULL(#FirstNameLocal,'')=''
THEN N''
ELSE N' AND CONTAINS(FirstName, #FirstNameLocal)'
END +
CASE WHEN ISNULL(#LastNameLocal,'')=''
THEN N''
ELSE N' AND CONTAINS(LastName, #LastNameLocal)'
END + ';'
EXEC sp_executesql
#stmt,
N'#FirstNameLocal VARCHAR(256),#LastNameLocal VARCHAR(256)',
#FirstNameLocal,
#LastNameLocal;
The downside is that the statement is compiled again each time this script is run, but this will be small compared to the benefit of full-text indexes that can be used in this statement.
Always compare the Actual Execution Plans to choose which version is best.