使用子查询插入多行答案

【问题标题】：insert multiple rows using subquery使用子查询插入多行
【发布时间】：2012-12-11 23:34:35
【问题描述】：

这是查询：

INSERT INTO qualification_lookup (variation, correct_qualification)
SELECT (SELECT Qualification FROM student WHERE Qualification like 'A%') ,'A-Level'

这是我尝试执行查询时遇到的错误。

消息 512，级别 16，状态 1，行 1 子查询返回超过 1 个值。当子查询跟随 =、!=、、>= 或子查询用作表达式时，这是不允许的。声明已终止。

如果有人告诉我任何替代方法，那么我是 SQL 新手。

【问题讨论】：

标签： sql sql-server database

【解决方案1】：

INSERT INTO qualification_lookup (variation, correct_qualification) 
select Qualification,'A-Level' from student   where Qualification like 'A%'

【讨论】：

【解决方案2】：

    INSERT INTO qualification_lookup (variation, correct_qualification) 
select Qualification, 'A-Level' from student where Qualification like 'A%'

语法是否正确

【讨论】：

【解决方案3】：

您需要考虑如何构建查询 - 考虑一下如果您只运行此代码会得到什么：

 SELECT (select Qualification from student where Qualification like 'A%') ,'A-Level'

你得到的确切错误将是我的猜测 - 你有一个试图与单个字符串匹配的许多资格的列表 - 'A-level'。

另一方面，这会很好用

 select Qualification, 'A-Level' from student where Qualification like 'A%'

在我看来，INSERT 和 UPDATE 语句的诀窍是编写一个 SELECT 语句来满足您的需求，然后将其包装起来

INSERT INTO qualification_lookup (variation, correct_qualification) select Qualification, 'A-Level' from student where Qualification like 'A%'

【讨论】：

【解决方案4】：

问题是这个子查询：

select Qualification from student where Qualification like 'A%'

返回几行。这就是您收到错误消息 512 的原因

不需要使用它。

这就够了：

INSERT INTO qualification_lookup (variation, correct_qualification) 
select Qualification, 'A-Level' as correct_qualification
from student where Qualification like 'A%'

【讨论】：

【解决方案5】：

declare @count int
declare @index int = 1
declare @currentQualificationId int = null

set @count = (select distinct count(QualificationId) from Qualification  from  where 
Qualification like 'A%')

set @currentQualificationId = (SELECT QualificationId from (select QualificationId , 
ROW_NUMBER() OVER (ORDER BY QualificationId) AS RowNumber from Qualification where 
Qualification like 'A%') as Qualification
where Qualification.RowNumber = @index) 


while (@index <= @count)
 begin

    INSERT INTO qualification_lookup (variation, correct_qualification) 
     values((select Qualification where QualificationId = 
     @currentQualificationId),'A-Level')

    set @index = @index + 1

     set @currentQualificationId = (SELECT QualificationId from (select 
     QualificationId , ROW_NUMBER() OVER (ORDER BY QualificationId) AS RowNumber from 
     Qualification where Qualification like 'A%') as Qualification
     where Qualification.RowNumber = @index) 
END

【讨论】：