The following joined update updates a table called data.dbo.table1 from a table called data.dbo.table2 and sets the fielda in table1 equal to fielda in table2 based on a matching ref:
updatedata.dbo.table1
setfielda = b.fielda
fromdata.dbo.table1 as a
joindata.dbo.table2 as b
on a.ref = b.ref
