Question

我正在尝试使用连接更新表格。任务是：修改数据库以显示Helen Partou现在已经学会充分播放手鼓。

这是我的尝试：

update MusicianInstrument
set instrumentName = 'Tambourine',levelOfExpertise = 'Adequate'
from MusicianInstrument  join Musician
on MusicianInstrument.musicianNo = Musician.musicianNo
where musicianName = 'Helen Partou';

但是我一直在使用FROM语句错误.....任何帮助？！

谢谢

Answer 1

您想使用WHERE EXISTS：

UPDATE MusicianInstrument mi
   SET mi.instrumentName = 'Tambourine'
     , mi.levelOfExpertise = 'Adequate'
 WHERE EXISTS ( SELECT 1 FROM Musician m
                 WHERE m.musicianNo = mi.musicianNo
                   AND m.musicianName = 'Helen Partou');

在您注意使用Oracle之后，我建议不要使用CamelCase或无头CamelCase作为对象名称。

Answer 2

您的任务是修改数据库，因此不仅可能更新表，还可以插入值（如果它们尚未存在）。您可以使用merge：

执行此操作

merge into MusicianInstrument i
using (select * from Musician where musicianName = 'Helen Partou') m
on (m.musicianNo = i.musicianNo 
  and i.instrumentName = 'Tambourine')
when matched then update set levelOfExpertise = 'Adequate'
when not matched then insert (i.musicianNo, i.instrumentName, i.levelOfExpertise)
   values (m.musicianNo, 'Tambourine', 'Adequate')

加入两个表时更新查询？

2 个答案: