I am trying to update and
update
set=
(select ....);

and in my select returns more than 1 rows(MSGubquery returns more than 1 rows).
For example if there are more than one same value in a cell that matches with select (4,4,4,4,4,4,4...) i want to put only the '4' in the value and not all the 4's!Thats why it hits an error but i dont know how to put only one of the same values in the cell.
Any idea?

Use limit statement in your subquery to select the first record alone

Syntax:

UPDATE <tablename>
SET <colname> = (SELECT <colname> FROM <tablename> LIMIT 1);