更新问题 [英] Problem for Update

问题描述

我有一个表行(ID，LineNo，LineName)，其值为:

I have a table line (ID, LineNo, LineName) having values as :

1, 1, <blank>
2, 2, <blank>
3, 3, <blank>

现在，我必须编写一个查询，以使其更新来自空白表(如上显示为< blank>)的行表中的LineName列，其值来自表linet(linenamet)的值为:

Now i have to write a query such that it updates LineName column from line table which is blank(as shown above with <blank>) with values from table linet(linenamet) having values as :

a
b
c

我的试用查询是:
更新行集LineName =(从linet中选择linenamet)；

它给出错误为:子查询返回多于1行"

预期结果:
更新后，它应将行表显示为:

My trial query is :
update line set LineName = (select linenamet from linet);

It gives error as : "Subquery returns more than 1 row"

Expected Result:
After Updation it should show line table as:

1, 1, a
2, 2, b
3, 3, c

请让我知道相同的更新SQL查询.

感谢和问候，

Kindly let me know the update SQL query for the same.

Thanks and Regards,

推荐答案

以下查询您所写的内容将导致您明确指出的错误，因为从linet中获取的行数多于一个linenamet，对于你就是例子.

更新行集LineName =(从linet中选择linenamet)；

为此，您可以像这样修改查询.

Following query what you''ve written will cause error you stated definately because you are getting more then one linenamet from linet, That is 3 for you example.

update line set LineName = (select linenamet from linet);

For that you can modify your query like.

update line set LineName = (select linenamet from linet --include some condition which gives you exact single result from corrosponding table)

如果linenamet表中只有一列，那么我认为是无法获取的.

If there''s a single column in linenamet table then I think it is not possible to fetch.

如果您的表行也有一个主键来链接它(外部键)到表行中的ID或LineNo，它看起来像这样
linet中名为ID的列是引用行列ID的外键:

If your table linet also had a primary key to it that would link it (foreign key) to a either ID or LineNo in table line it would look like this
Column named ID in linet is foreign key referencing line column ID:

UPDATE line SET LineName = (SELECT linenamet FROM linet ln WHERE ln.ID = line.ID)

linet中名为ID的列是引用表行列LineNo的外键:

Column named ID in linet is foreign key referencing table line column LineNo:

UPDATE line SET LineName = (SELECT linenamet FROM linet ln WHERE ln.LineNo = line.ID)

由于我们不知道表linet是否具有任何外键或您根本不需要告诉我们的任何键.也许有第三个表使表之间的关系为线和线.

最好的问候，
曼弗雷德(Manfred)

Since we don''t know if table linet has any foreign key or any key at all you need to tell us. Maybe there is a third table that makes the relation between the tables linet and line.

Best Regards,
Manfred

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