sql 技巧

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• update时连表

https://stackoverflow.com/questions/1293330/how-can-i-do-an-update-statement-with-join-in-sql

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

SQLite:
update ud 
     set assid = (
          select sale.assid 
          from sale 
          where sale.udid = ud.id
     )
 where RowID in (
      select RowID 
      from ud 
      where sale.udid = ud.id
 );