The Filtered Index was introduced in MS SQL Server 2008. In this article, we are not directly discussing the Filtered Index, but solving some common queries related to the Filter Index.
An Example of Filtered Index
-- Base table IF OBJECT_ID(N'dbo.tbl_EMPLOYEE', N'U') IS NOT NULL BEGIN DROP TABLE [dbo].[tbl_EMPLOYEE]; END GO CREATE TABLE [dbo].[tbl_EMPLOYEE] (EMPID INT NOT NULL IDENTITY PRIMARY KEY, EMPNAME VARCHAR(50) NOT NULL, DOB DATE NOT NULL, GRADE CHAR(1) NOT NULL); GO -- Inserting Records INSERT INTO [dbo].[tbl_EMPLOYEE] (EMPNAME, DOB, GRADE) VALUES('Joydeep Das', '1974-12-17', 'A'), ('Jukamal Jana','1974-10-11', 'A'), ('Chandan Bannerjee','1973-06-09', 'B'), ('Soumen Bhomik', '2008-11-28', 'C'); GO -- Create Filtered Index CREATE NONCLUSTERED INDEX IX_NON_GRADE_tbl_EMPLOYEE ON [dbo].[tbl_EMPLOYEE](GRADE) WHERE GRADE = 'A';
Now we are trying to solve some Query
Query – 1
What Type of Comparison operator used in Filter Criteria in Filtered Index
|IS NOT NULL|
Query – 2
Is BETWEEN Clause is used in Filter Criteria of Filtered Index
NO. The BETWEEN Clause is not used in Filter Criteria of FILTERED Index. We can use >= and <= to get the output like BETWEEN Clause.
CREATE NONCLUSTERED INDEX IX_NON_GRADE_tbl_EMPLOYEE ON [dbo].[tbl_EMPLOYEE](GRADE) WHERE DOB >= '1974-01-01' AND DOB <= '1974-12-31';
Query – 3
Is it possible to add more data to Filtered Index without dropping and re-creating it
Yes it is possible.
Query – 4
Can we use the SUB QUERY in the Filtered Index WHERE Clause like
WHERE Grate=(SELECT grade FROM tbal_2)
NO it is not Possible. WHERE Clause of Filtered Index always needs a Scalar value.
As per MSDN
Under the "WHERE" section of the Arguments heading:
The filter predicate uses simple comparison logic and cannot reference a computed column, a UDT column, a spatial data type column, or a hierarchyID data type column. Comparisons using NULL literals are not allowed with the comparison operators. Use the IS NULL and IS NOT NULL operators instead.
If you have any question in mind related to FILTERED INDEX please make some comments to solve it.
Hope you like it.