Update Statement Between Two Tables

Hi,

I have a table with the Following fields City, Txns in the table BOB_BK. There is another table "SUM_MONTH" with the same two fields with some additional information. Now I want to get Value in the field TXNS of BOB_BK in "SUM_MONTH" Table. But when i write the following query

UPDATE SUM_MONTH A
SET A.TXNS = B.TXNS FROM BOB_BK B, SUM_MONTH A
WHERE A.CITY = B.CITY... It gives me a error saying SQL not complete. Then I Tried the following query

UPDATE SUM_MONTH A
SET A.TXNS = (SELECT B.TXNS FROM
BOB_BK B, SUM_MONTH A
WHERE B.CITY = A.CITY).. It gives an error saying subquery returning more than one value. but if i remove the = sign and replace it by IN it still gives as error saying "= sign missing". So how do i run this update???

Thanks in Advance
Suresh

THis is not working.Still gives me an error ORA-01427: single-row subquery returns more than one row.

The latest Query...
UPDATE SUM_MONTH A
SET A.TXN_COUNT_M = (SELECT b.TRNS
FROM BOB_BK B
WHERE A.N_CITY_CODE = B.N_CITY_CODE
AND A.BANK_CODE = '00001')
WHERE N_CITY_CODE in (select N_CITY_CODE from bob_bk);

Can you suggest something else...

So, for some cities in the SUM_MONTH tables there are multiple records in the BOB_BK table. Which of those rows shall you choose? Or should you do an aggregation instead? It's your choice.

Obviously I had to use the aggregate function. and it worked. Thanks a lot for your help buddy... Helped me restore the data in the production server. Thanks a million again.....