nested group function

[latha9]

Hi,

I need to find the count according to some conditions.i have written the following query and i got the result.
select distinct i.INS_ID ,
count(CASE WHEN va.ANSWER <> 'CSS' or va.ANSWER <> 'RS' THEN 1 end) "Already in Treatment",
count(CASE WHEN va.ANSWER = 'CSS' THEN 1 end) "New to Treatment - CSS Only",
count(CASE WHEN va.ANSWER <> 'RS' THEN 1 end) "New to Treatment- RS Only",
count(CASE WHEN va.ANSWER = 'CSS' and va.ANSWER = 'RS' THEN 1 end) "New to Treatment - CSS and RS" ,
count(CASE WHEN (va.ANSWER <> 'CSS' or va.ANSWER <> 'RS') and pxa.ASSOC_ID=18 THEN 1 end) "CM AIL",
count(CASE WHEN (va.ANSWER <> 'CSS' or va.ANSWER <> 'RS') and pxa.ASSOC_ID !=18 THEN 1 end) "NCM AIL",
count(CASE WHEN va.ANSWER = 'CSS' and pxa.ASSOC_ID=18 THEN 1 end) "CM CSS",
count(CASE WHEN va.ANSWER = 'CSS' and pxa.ASSOC_ID !=18 THEN 1 end) "NCM CSS",
count(CASE WHEN va.ANSWER <> 'RS' and pxa.ASSOC_ID=18 THEN 1 end) "CM RS ",
count(CASE WHEN va.ANSWER <> 'RS' and pxa.ASSOC_ID !=18 THEN 1 end) "NCM RS" ,
count(CASE WHEN va.ANSWER = 'CSS' and va.ANSWER = 'RS' and pxa.ASSOC_ID=18 THEN 1 end) "CM NTT",
count(CASE WHEN va.ANSWER = 'CSS' and va.ANSWER = 'RS' and pxa.ASSOC_ID!=18 THEN 1 end) "NCM NIT"


from instrument i,dept_assessment da,v_assessment_answer
va,people_x_association pxa,association a
where pxa.PEO_ID= va.peo_id
and pxa.END_DATE is null
and a.assoc_id= pxa.ASSOC_ID
and a.assoc_id in (100,102,182,183,184,185)
and i.INS_NAME = 'MH Enrollment And Certification CSS RS'
and da.INS_ID=i.INS_ID
and va.INS_ID= i.INS_ID
and va.ASSMT_ID=da.ASSMT_ID
and va.INS_QUES_GRID_NAME= 'IF CONSUMER NEW TO SERVICE:'
and va.DATE_START >=to_date('01/18/2004','mm/dd/yyyy') and va.DATE_START <= to_date('02/10/2006','mm/dd/yyyy')
and va.DATE_END is null
group by i.INS_ID

now what i have to do is i have to find the sum of already in treatment ,new to treatment - css only ,new to treatment-RS only and new to treatment- css and rs only.
Is it possible to do it in a single SQL statement.
I have written a query in the following way.
select distinct i.INS_ID ,
count(CASE WHEN va.ANSWER <> 'CSS' or va.ANSWER <> 'RS' THEN 1 end) "Already in Treatment",
count(CASE WHEN va.ANSWER = 'CSS' THEN 1 end) "New to Treatment - CSS Only",
count(CASE WHEN va.ANSWER <> 'RS' THEN 1 end) "New to Treatment- RS Only",
count(CASE WHEN va.ANSWER = 'CSS' and va.ANSWER = 'RS' THEN 1 end) "New to Treatment - CSS and RS" ,
count(CASE WHEN (va.ANSWER <> 'CSS' or va.ANSWER <> 'RS') and pxa.ASSOC_ID=18 THEN 1 end) "CM AIL",
count(CASE WHEN (va.ANSWER <> 'CSS' or va.ANSWER <> 'RS') and pxa.ASSOC_ID !=18 THEN 1 end) "NCM AIL",
count(CASE WHEN va.ANSWER = 'CSS' and pxa.ASSOC_ID=18 THEN 1 end) "CM CSS",
count(CASE WHEN va.ANSWER = 'CSS' and pxa.ASSOC_ID !=18 THEN 1 end) "NCM CSS",
count(CASE WHEN va.ANSWER <> 'RS' and pxa.ASSOC_ID=18 THEN 1 end) "CM RS ",
count(CASE WHEN va.ANSWER <> 'RS' and pxa.ASSOC_ID !=18 THEN 1 end) "NCM RS" ,
count(CASE WHEN va.ANSWER = 'CSS' and va.ANSWER = 'RS' and pxa.ASSOC_ID=18 THEN 1 end) "CM NTT",
count(CASE WHEN va.ANSWER = 'CSS' and va.ANSWER = 'RS' and pxa.ASSOC_ID!=18 THEN 1 end) "NCM NIT" ,
sum(count(CASE WHEN va.ANSWER <> 'CSS' or va.ANSWER <> 'RS' THEN 1 end)+
count(CASE WHEN va.ANSWER = 'CSS' THEN 1 end)+count(CASE WHEN va.ANSWER <> 'RS' THEN 1 end)+
count(CASE WHEN va.ANSWER = 'CSS' and va.ANSWER = 'RS' THEN 1 end)) "total"



from instrument i,dept_assessment da,v_assessment_answer
va,people_x_association pxa,association a
where pxa.PEO_ID= va.peo_id
and pxa.END_DATE is null
and a.assoc_id= pxa.ASSOC_ID
and a.assoc_id in (100,102,182,183,184,185)
and i.INS_NAME = 'MH Enrollment And Certification CSS RS'
and da.INS_ID=i.INS_ID
and va.INS_ID= i.INS_ID
and va.ASSMT_ID=da.ASSMT_ID
and va.INS_QUES_GRID_NAME= 'IF CONSUMER NEW TO SERVICE:'
and va.DATE_START >=to_date('01/18/2004','mm/dd/yyyy') and va.DATE_START <= to_date('02/10/2006','mm/dd/yyyy')
and va.DATE_END is null
group by i.INS_ID

but i am getting an error ORA-00937 (not a single-group group function).

Can anyone suggest me how can i do this.please it's very urgent.

Thanks,