Search from Multiple columns in Where clause for SQL Server - sql

Question

We have a stored procedure that is used to allow users to search in a table with 20 million records and 40 columns wide. There are about 20 different columns they can search on (any combination) from and all those columns are in the WHERE clause.
Furthermore each columns is checked for Null and needs to be able to search with just part of the data.
Here is an example
(
#FirstName IS NULL
OR (RTRIM(UPPER(FirstName)) LIKE RTRIM(UPPER(#FirstName)) + '%')
)
AND (#LastName IS NULL)
What is a best way to rewrite this stored procedure? Should I break this stored procedure into multiple small stored procedures? If so how? I will need to allow user to search
When I look at the execution plan, regardless of what columns are passed, it always does the index scan

Answer 1

I had exactly this situation years ago, millions of rows and numerous filter parameters and the best method is to use dynamic sql. Construct a SQL statement based on the parameters that have values, then execute the SQL statement. (EXEC sp_executesql #sql)
The select clause of the sql statement is static but the from clause and the where clause is based on the parameters.
CREATE PROCEDURE dbo.DynamicSearch
#FirstName VARCHAR(20),
#LastName VARCHAR(20),
#CompanyName VARCHAR(50)
AS
BEGIN
DECLARE #SQL NVARCHAR(MAX) = N''
DECLARE #Select NVARCHAR(MAX) = N'SELECT ColA, ColB, ColC, ColD '
DECLARE #From NVARCHAR(MAX) = N'From Person'
DECLARE #Where NVARCHAR(MAX) = N''
IF #FirstName IS NOT NULL
Begin
Set #Where = #Where + 'FirstName = ''' + #FirstName + ''''
End
IF #LastName IS NOT NULL
Begin
if len(#Where) > 0
Begin
Set #Where = #Where + ' AND '
End
Set #Where = #Where + 'LastName = ''' + #LastName + ''''
End
IF #CompanyName IS NOT NULL
Begin
if len(#Where) > 0
Begin
Set #Where = #Where + ' AND '
End
Set #From = #From + ' inner join Company on person.companyid = company.companyid '
Set #Where = #Where + 'company.CompanyName = ''' + #CompanyName + ''''
End
Set #SQL = #Select + #From + #Where
EXECUTE sp_executesql #sql
END

Answer 2

To go down the dynamic SQL route you would use something like:
CREATE PROCEDURE dbo.SearchSomeTable
#FirstName VARCHAR(20),
#LastName VARCHAR(20),
#AnotherCol INT
AS
BEGIN
DECLARE #SQL NVARCHAR(MAX) = N'SELECT SomeColumn FROM SomeTable WHERE 1 = 1',
#ParamDefinition NVARCHAR(MAX) = N'#FirstName VARCHAR(20),
#LastName VARCHAR(20),
#AnotherCol INT';
IF #FirstName IS NOT NULL
#SQL = #SQL + ' AND FirstName = #FirstName';
IF #LastName IS NOT NULL
#SQL = #SQL + ' AND LastName = #LastName';
IF #AnotherCol IS NOT NULL
#SQL = #SQL + ' AND AnotherCol = #AnotherCol';
EXECUTE sp_executesql #sql, #ParamDefinition, #FirstName, #LastName, #AnotherCol;
END
Otherwise you will need to use the OPTION (RECOMPILE) query hint to force the query to recompile each time it is run to get the optimal plan for the particular parameters you have passed.

Answer 3

Another possibility, though the above is perhaps the most logical, is to create one or more "search" criteria tables into which you insert the users selections, and then perform LEFT JOINS against the search criteria. You would only be able to do this for cases in which there is an equivalency and preferably an small datatype such as int. For string comparisons, these kind of joins would be potentially dreadful as far as performance goes. The only problem with the above suggestion (dynamic-sql) is the possibility of plan cache bloat as each execution in which there is only one difference with an existing plan would cause a new plan to be generated.