Thanks For the Good Question Tom Brown i learnt some thing new today and also i tried to create index on the computed columns it will not alllow to create index directly.

and i tried in this way

PRINT 'Define Table';

CREATE TABLE #Quantities (

ID INT IDENTITY,

DataSource varchar(30) NOT NULL,

QF1 Float,

QF2 Float,

QTot AS QF1 + QF2,

PF1 AS QF1 / (QF1 + QF2),

PF2 AS QF2 / (QF1 + QF2) );

CREATE NONCLUSTERED INDEX IXC1 on #Quantities(ID) INCLUDE(PF1,PF2)

PRINT 'Insert data';

INSERT INTO #Quantities (DataSource, QF1, QF2)

SELECT 'Test 1' , 66, 34;

Print 'Insert Zeroes';

INSERT INTO #Quantities (DataSource, QF1, QF2)

SELECT 'Test 2', 0, 0;

Print 'Insert Nulls';

INSERT INTO #Quantities (DataSource, QF1, QF2)

SELECT 'Test 3', null, null;

PRINT 'Show Table';

SELECT * FROM #Quantities;

DROP TABLE #Quantities

i got the error while inserting the value it self

thanks again for the Good question