SQL UPDATE using a JOIN

There are a few different ways to update a “source table” by joining it to another table.

 

ANSI/ISO:

update ud 
  set assid = (
               select sale.assid 
                 from sale 
                where sale.udid = ud.id
              )
 where exists (
               select * 
                 from sale 
                where sale.udid = ud.id
              );

 

MySQL:

update ud u
inner join sale s on
    u.id = s.udid
set u.assid = s.assid

 

SQL Server:

update u
set u.assid = s.assid
from ud u
    inner join sale s on
        u.id = s.udid

 

Oracle:

update
    (select
        u.assid as new_assid,
        s.assid as old_assid
    from ud u
        inner join sale s on
            u.id = s.udid) up
set up.new_assid = up.old_assid