Update statement using select and group by throwing missing expression - sql

Question

I tried to update a table column deletiondate with data from another table but I get "missing expression" error. Can someone help me resolve this issue?
Basically I want to update deletiondate column in a table by joining the key fields with another table and doing a group by. If the date is 01-JAN-0001 and count of records is > 1 then need to update 01-JAN-0001 else I need to update the maximum deletion date value.
The update Statement I used:
update table1 db1 set deletiondate =
SELECT
CASE WHEN count(*)>1 and (
(select 1
from table2 b
where b.loginid = a.loginid
and a.creationdate = b.creationdate
and b.deletiondate = '01-JAN-0001'
) = 1) THEN '01-JAN-0001' ELSE to_char(MAX(deletiondate),'DD-MON-YYYY') END as deletiondate1
FROM table2 a
GROUP BY a.loginid, a.creationdate
WHERE db1.userloginid = a.loginid and db1.usercreationdate = a.creationdate

Answer 1

Use this format: http://www.sqlfiddle.com/#!4/c46a6/2
update product set
(total_qty,max_qty) =
(
select sum(qty) as tot, max(qty) as maxq
from inv
where product_id = product.product_id
group by product_id
) ;
Sample data:
create table product(
product_id int primary key,
product_name varchar(100),
total_qty int,
max_qty int
);
create table inv(
inv_id int primary key,
product_id int references product(product_id),
qty int
);
insert into product(product_id,product_name)
select 1,'KB' from dual
union
select 2, 'MSE' from dual
union
select 3, 'CPU' from dual;
insert into inv(inv_id,product_id,qty)
select 1,1,4 from dual
union
select 2,2,1 from dual
union
select 3,3, 3 from dual
union
select 4,1,1 from dual
union
select 5,2,2 from dual
union
select 6,1,5 from dual;
Query output:
| PRODUCT_ID | PRODUCT_NAME | TOTAL_QTY | MAX_QTY |
|------------|--------------|-----------|---------|
| 1 | KB | 10 | 5 |
| 2 | MSE | 3 | 2 |
| 3 | CPU | 3 | 3 |