Question

I have some null values in my table, I have to update that values from other table. I am using the following query but the sub query returns more than one value.

update student st 
set n_id=(select n_id 
          from class cl 
          where st.uid=cl.uid 
          and ( cl.start_date='31-jan-2011' or cl.start_date='28-feb-2011') 
          and st.n_id is null);

How can I update my field. Help me to find out. Thanks.

Answer 1

you could either work on the logic or add the statement

and rownum = 1

then your subquery will always return just one row (the first one.. if it exists)