将父表中的每一行插入到子表中

Question

我的数据库看起来像这样，

tblAudits
PK AuditID
AuditStatus nvarchar(50)

tblQuestionDefs
PK QuestionID

tblAuditAnswers
PK AnswerID
FK AuditID
FK QuestionID

我最近在审核中添加了一些新问题，并且我想为所有活动审核中的每个新问题添加答案记录。在 SQL 中执行此操作的最佳方法是什么？我知道我可以使用游标或循环，但据我所知，这些都非常慢。有什么基于集合的方法吗？

这是基于光标的代码

declare
    @AuditID int

declare AuditsCursor cursor fast_forward for
    select AuditID from tblAudits where AuditStatus='Issued' or AuditStatus='Pending' order by AuditID desc

open AuditsCursor
fetch next from AuditsCursor
into @AuditID

while @@FETCH_STATUS = 0
begin

    insert into tblAuditAnswers (AuditID, QuestionID)
    select @AuditID as AuditID, QuestionID
    from tblQuestionDefs
    where QuestionID not in (
        select QuestionID from tblAuditAnswers where AuditID=@AuditID
    )

fetch next from AuditsCursor
into @AuditID
end

close AuditsCursor
deallocate AuditsCursor

Answer 1

insert into tblAuditAnswers (AuditID, QuestionID)
select A.AuditID, QD.QuestionID
from tblAudits as A
  cross join tblQuestionDefs as QD
where (A.AuditStatus='Issued' or A.AuditStatus='Pending') and
        not exists (select *
                    from tblAuditAnswers as AA
                    where QD.QuestionID = AA.QuestionID and
                          A.AuditID = AA.AuditID)

https://data.stackexchange.com/stackoverflow/q/123061/

Answer 2

INSERT INTO tblAuditAnswers
            (AuditID,
             QuestionID)
SELECT A.AuditID,
       Q.QuestionID
FROM   tblAudits A
       CROSS JOIN (SELECT QuestionID
                   FROM   tblQuestionDefs
                   EXCEPT
                   SELECT QuestionID
                   FROM   tblAuditAnswers) Q
WHERE  A.AuditStatus IN ( 'Issued', 'Pending' ) 

Answer 3

不需要游标。

INSERT INTO tblAuditAnswers
    (AuditID, QuestionID)
SELECT
    A.AuditID, Q.QuestionID
FROM
    tblAudits A
    CROSS JOIN tblQuestionDefs Q
    LEFT JOIN tblAuditAnswers AA
        ON A.AuditID = AA.AuditID AND Q.QuestionID = AA.QuestionID
WHERE
    A.AuditStatus='Issued' OR A.AuditStatus='Pending' AND
    AA.AuditID IS NULL
ORDER BY
    A.AuditID DESC

如果问题定义与特定审核类型相关，那么您还应该将 CROSS JOIN 替换为 INNER JOIN：

INNER JOIN tblQuestionDefs Q
    A.AuditTypeID = Q.AuditTypeID