Excel ADODB Sql Query Execution taking hours when manipulate excel tables

Question

Hello All 
I have 28000 records with 8 column in an sheet. When I convert the sheet into ADODB database and copy to new
excel using below code it is executing in less than a min
Set Tables_conn_obj = New ADODB.Connection
Tables_conn_str = "Provider=Microsoft.ACE.OLEDB.12.0;Data Source=" & Table_Filename & ";Extended Properties=""Excel 12.0;ReadOnly=False;HDR = Yes;IMEX=1"""
Tables_conn_obj.Open Tables_conn_str
First_Temp_sqlqry = "Select * INTO [Excel 12.0;DATABASE=C:\Prod Validation\Database\Second Acat Table.xlsb].[Sheet1] Table [first - Table$];" Tables_conn_obj.Execute First_Temp_sqlqry
But when I change the query to manipulate one column in current table based on another table in the same excel
and try to copy the results in another excel, it is taking more than one hour.. why it is taking this much time when both the query results returns the same number of rows and column. I almost spend one week and still not able to resolve this issue.
Even I tried copyfromrecordset, getrows(), getstring(), Looping each recordset fields options all of them taking
same amount of time. Why there is huge difference in execution time.
Important note: Without into statement even below query is executing in few seconds.
select ( ''''''manipulating first column based on other table data''''''''''''''
iif(
[Second - Table$].[Policy Agent] = (select max([ACAT$].[new_Agent_number]) from [ACAT$] where [ACAT$].[new_Agent_number] = [Second - Table$].[Policy Agent] and [ACAT$].[ACAT_EffectiveDate] = ( select MAX([ACAT$].[ACAT_EffectiveDate] ) from [ACAT$] where [ACAT$].[new_Agent_number] = [Second - Table$].[Policy Agent]and [ACAT$].[ACAT_EffectiveDate] > '2014-10-01') ) , (select max([ACAT$].[Old_Agent_number]) from [ACAT$] where [ACAT$].[new_Agent_number] = [Second - Table$].[Policy Agent] and [ACAT$].[ACAT_EffectiveDate] = ( select MAX([ACAT$].[ACAT_EffectiveDate] ) from [ACAT$] where [ACAT$].[new_Agent_number] = [Second - Table$].[Policy Agent]and [ACAT$].[ACAT_EffectiveDate] > '2014-10-01')) ,
iif( [Second - Table$].[Policy Agent] = (select max([ACAT$].[Old_Agent_number]) from [ACAT$] where [ACAT$].[Old_Agent_number] = [Second - Table$].[Policy Agent] and [ACAT$].[ACAT_EffectiveDate] = ( select MAX([ACAT$].[ACAT_EffectiveDate] ) from [ACAT$]where [ACA T$].[Old_Agent_number] = [Second - Table$].[Policy Agent]and [ACAT$].[ACAT_EffectiveDate] <= '2014-10-01') ), (select max([ACAT$].[new_Agent_number]) from [ACAT$] where [ACAT$].[Old_Agent_number] = [Second - Table$].[Policy Agent] and [ACAT$].[ACAT_EffectiveDate] = ( select MAX([ACAT$].[ACAT_EffectiveDate] ) from [ACAT$] where [ACAT$].[Old_Agent_number] = [Second - Table$].[Policy Agent]and [ACAT$].[ACAT_EffectiveDate] <= '2014-10-01')) ,
[Second - Table$].[Policy Agent] ))) as [Policy Agent],
''''''summing up all other columns''''''''''''''
(iif(isnull(sum([Second - Table$].[Auto BW-Line Of Business Detail])),0,sum([Second - Table$].[Auto BW-Line Of Business Detail]))) as [Auto BW-Line Of Business Detail],(iif(isnull(sum([Second - Table$].[Auto Farmers])),0,sum([Second - Table$].[Auto Farmers]))) as [Auto Farmers],(iif(isnull(sum([Second - Table$].[MCA])),0,sum([Second - Table$].[MCA]))) as [MCA],(iif(isnull(sum([Second - Table$].[CEA])),0,sum([Second - Table$].[CEA]))) as [CEA],(iif(isnull(sum([Second - Table$].[Commercial P&C])),0,sum([Second - Table$].[Commercial P&C]))) as [Commercial P&C],(iif(isnull(sum([Second - Table$].[Comm WC])),0,sum([Second - Table$].[Comm WC]))) as [Comm WC],(iif(isnull(sum([Second - Table$].[Fire Farmers])),0,sum([Second - Table$].[Fire Farmers]))) as [Fire Farmers],(iif(isnull(sum([Second - Table$].[Flood])),0,sum([Second - Table$].[Flood]))) as [Flood],(iif(isnull(sum([Second - Table$].[Kraft Lake])),0,sum([Second - Table$].[Kraft Lake]))) as [Kraft Lake],(iif(isnull(sum([Second - Table$].[Life])),0,sum([Second - Table$].[Life]))) as [Life],(iif(isnull(sum([Second - Table$].[Foremost])),0,sum([Second - Table$].[Foremost]))) as [Foremost],(iif(isnull(sum([Second - Table$].[Umbrella])),0,sum([Second - Table$].[Umbrella]))) as [Umbrella],(iif(isnull(sum([Second - Table$].[MCNA])),0,sum([Second - Table$].[MCNA]))) as [MCNA]
INTO [Excel 12.0;DATABASE=C:\Prod Validation\Database\Second Acat Table.xlsb].[Sheet1]
from [Second - Table$] group by [Second - Table$].[Policy Agent] ;

Answer 1

Hi Fei,
  Thank you so much for the reply post. I just executed the same above SQL without INTO Statement and assigned the SQL result to ADODB recordset as below. If the time difference is due to the SQL query then below statements also should execute for hours
right, but it gets executed in seconds. But to copy the recordset to excel again it is taking hours. I tried copyfromrecordset,
getrows(), getstring(), Looping each recordset fields options and all of them taking same amount of time. Please let me know there is delay in time for this much small data
Even I tried to typecast all columns to double, string in SQL and still the execution time  is not reduced. 
First_Temp_Recordset.Open sql_qry, Tables_conn_obj, adOpenStatic, adLockOptimistic ''' OR SET First_Temp_Recordset = Tables_conn_obj.Execute sql_qry