按此顺序根据主 ID 更新列
这是测试代码。我希望更新 city_id，以便 city_id 必须与 select 语句中出现的该城市的第一个 id 匹配。例子。在这里，我希望 city_id [最后一列] 为 1,1,3,3
create table student2 (id int not null primary key identity,
city_name varchar(25),
student_name varchar(25),
city_id int null)
insert into student2 values('Boston','Nome',null)
insert into student2 values('Boston','Tiger',null)
insert into student2 values('Miami','Andy',null)
insert into student2 values('Miami','Moran',null)
两个查询是如果这样就可以了。我显然有大量记录。创建临时表并将结果输出到文本文件也可以。在这种情况下，您将打印 id 和 city_id
Here is the test code. I would like the city_id to be updated such that the city_id must must match the first id of that city that appears in select statement. Example. Here I would like the city_id [last column] to be 1,1,3,3
create table student2 (id int not null primary key identity,
city_name varchar(25),
student_name varchar(25),
city_id int null)
insert into student2 values('Boston','Nome',null)
insert into student2 values('Boston','Tiger',null)
insert into student2 values('Miami','Andy',null)
insert into student2 values('Miami','Moran',null)
Two query's are fine if that does the job. I have obviously large number of records. Creating temporary table and outputting the result to text file is fine too. In that case you would print id and city_id
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最好的方法是创建一个名为
cities的新表，其中包含列city_id和city_name。这称为规范化数据库，并降低问题的复杂性。对于您的示例，您将拥有：
The best approach is to create a new table called
cities, that contains columnscity_idandcity_name. This is called normalizing the database, and reduces the complexity of your problem.For your example, you would have:
就像这样：
祝你好运！
Like this:
Good luck!