My Query returns this error ORA-01427: single-row subquery returns more than one row update, This is my query
Update Table_b B
Set B.Material_Desc = (Select A.Ma
The problem is your subquery is returning a whole bunch of rows where you should have only one. You can't do this like this.
Depending on the SQL database you're using, something like this should work better :
UPDATE Table_b B
SET B.Materiel_Desc = A.Materiel_Desc
INNER JOIN Table_a A ON A.PartNo = B.PartNo
It is possible you must adapt the syntax to your database. For example, I think you cannot do it like this with MySQL. According to http://dev.mysql.com/doc/refman/5.0/en/update.html you should do :
UPDATE Table_b, Table_A
SET Table_b.Materiel_Desc = Table_A.Materiel_Desc
WHERE Table_b.PartNo = Table_a.PartNo;