SQL更新与连接

Question

除了连接之外，还有其他更快的更新方式吗？这是我的查询，但有点慢:

UPDATE @user_dupes
  SET ExternalEmail = ud2.Email
 FROM @user_dupes ud1
INNER JOIN(
SELECT Email, UserName 
  FROM @user_flat_emailtable_dupes
 WHERE EmailType = 2
   AND Email IS NOT NULL AND LEN(Email) > 0
) ud2
ON ud1.UserName = ud2.UserName

感谢任何想法

Answer 1

如果您使用的是 SQL Server，那么您就快成功了。这只是一个小修复:

UPDATE ud1 --little fix here!
  SET ExternalEmail = ud2.Email
 FROM @user_dupes ud1
INNER JOIN
(
SELECT Email, UserName 
  FROM @user_flat_emailtable_dupes
 WHERE EmailType = 2
   AND Email IS NOT NULL AND LEN(Email) > 0
) ud2
ON ud1.UserName = ud2.UserName