Cannot create the clustered index '%.*ls' on view '%.*ls' because the select list of the view contains an expression on result of aggregate function or grouping column. Consider removing expression on result of aggregate function.

Error Message:
Msg 8668, Level 16, State 0, Line 2
Cannot create the clustered index '%.*ls' on view '%.*ls' because the select list of the view contains an expression on result of aggregate function or grouping column. Consider removing expression on result of aggregate function or grouping column from select list.

Severity level:
16.

Description:
This error message appears when you try to create a clustered index on a view, but the SELECT list contains an expression on the result of an aggregate function.

Consequences:
The T-SQL statement can be parsed, but causes the error at runtime.

Resolution:
Error of the Severity level 16 are generated by the user and are corrigible by the user. The statement cannot be run this way. Rewrite the view definition to eliminate the expression.

Versions:
This error message was introduced with SQL Server 2000.

Example(s):
SET NUMERIC_ROUNDABORT OFF;
SET ANSI_PADDING,
    ANSI_WARNINGS,
    CONCAT_NULL_YIELDS_NULL,
    ARITHABORT,
    QUOTED_IDENTIFIER,
    ANSI_NULLS ON;
GO

IF OBJECT_ID ('dbo.v', 'View') IS NOT NULL
   DROP VIEW dbo.v;
GO

IF OBJECT_ID('dbo.t') IS NOT NULL
    DROP TABLE dbo.t;
GO

CREATE TABLE dbo.t
(
    c1 int NOT NULL
);
GO

CREATE VIEW dbo.v
WITH SCHEMABINDING
AS
SELECT
   c1, SUM(c1) + 10 AS c2, COUNT_BIG(*) AS MyCount
FROM
    dbo.t T
GROUP BY
    T.c1;
GO

CREATE UNIQUE CLUSTERED INDEX cix_v
    ON dbo.v (c1);
GO

Remarks:
In the above example we try to create an expression to add 10 to the SUM() of c1. This raises the error.