query extracting over over 40,000,000 records

[YANECKC]

I have a query extracting information from three tables.
Table1 has 21,000 security numbers
Table2 has 50,000,000 security numbers and account numbers
Table3 has a OCCD field for each account number
Problem is after extracting the information there is over 40,000,000 records coming back.
The query keeps freezing on me. How can I run a query that only returns the subtotals for each OCCD field ? Meaning the new query should come back and tell me how many accounts for each OCCD.

 

[james_lankford]

what fields, besides OCCD, does table 3 have in it ?
does it have account number in it ?

 

[YANECKC]

Yes
Table3 has OCCD code and Account number

 

[YANECKC]

Table3 has about 20,000,000 records

 

[james_lankford]

hopefully its a simple as

select 
   [OCCD code], 
   count([Account number]) as CountOfAccountNumber
from 
  Table3
group by 
   [OCCD code]

but could take some time if those fields aren't indexed

 

[YANECKC]

My problem is first i have to extract from Table2 records that match the 21,000 security numbers and get the account numbers from Table2, which will be over 20,000,000 records . too large for output in a table for microsoft 2gig limit. Then from the account numbers on Table2 that the Securities appear in table1 i have to get the oocd codes from table3. That is why i only want the subtotals lines to come back.

Meaning the new query should come back and tell me how many accounts for each OCCD where the securities were match on Table1 and the accounts and securites were matched on table2.