我可以在一个语句中删除两个表中的条目吗？

Question

我必须从两个 table 中的每一个中删除一行，它们通过 ID 链接但没有正确的 PK - FK 关系（此数据库没有外键！）

table 之间具有假定的 1-1 关系。我不知道为什么不把它们放在同一个 table 但我不能随意更改它。

人

PersonId | Name | OwnsMonkey
----------------------------
    1       Jim       true
    2       Jim       false
    3       Gaz       true

信息

PersonId |    FurtherInfo
-----------------------------
    1       Hates his monkey
    2        Wants a monkey
    3       Loves his monkey

要决定删除什么，我必须找到一个用户名以及他们是否拥有一只猴子：

Select PersonId from People where Name = 'Jim' and OwnsMonkey = 'false'

所以我正在使用这个想法做两个单独的语句，先从 Info 中删除，然后从 People

中删除

delete from Info where PersonId = (Select PersonId from People where Name = 'Jim' and OwnsMonkey = 'false');

delete from People where PersonId = (Select PersonId from People where Name = 'Jim' and OwnsMonkey = 'false');

我找到了一个有希望的答案here on Whosebug

delete      a.*, b.*
from        People a
inner join  Info b
where       a.People = b.Info
            and a.PersonId = 
            (Select PersonId from People where Name = 'Jim' and OwnsMonkey = 'false')

但它在 Sql 服务器 (2012) 中给出了语法错误，我也尝试过不使用别名，但似乎无法同时删除两个 table

Answer 1

Can I delete entries from two tables in one statement?

没有。一条语句只能从 MS SQL 服务器中的一个 table 中删除行。

您提到的关于 MySQL 和 MySQL 的答案确实允许用一条语句从多个 table 中删除，如 MySQL docs. MS SQL Server doesn't support this, as can be seen in the docs.在 SQL 服务器的 DELETE 语句中没有包含多个 table 的语法。如果您尝试从视图中删除，而不是 table，也有一个限制：

The view referenced by table_or_view_name must be updatable and reference exactly one base table in the FROM clause of the view definition.

I was hoping to avoid two separate statements on the off-chance the second doesn't work for whatever reason, interrupted - concurrency really, I guess the TRY/CATCH will work well for that.

这就是交易的目的。您可以在一个事务中放置多个语句，它们要么都成功，要么都失败。全有或全无。

在你的情况下，你不仅可以，而且应该将两个 DELETE 语句都放在一个事务中。

TRY/CATCH 有助于以更可控的方式处理可能的错误，但主要概念是“事务”。

BEGIN TRANSACTION

delete from Info where PersonId = (Select PersonId from People where Name = 'Jim' and OwnsMonkey = 'false');

delete from People where PersonId = (Select PersonId from People where Name = 'Jim' and OwnsMonkey = 'false');

COMMIT

我强烈推荐阅读 Erland Sommarskog 的一篇很棒的文章 Error and Transaction Handling in SQL Server。

如果你想变得狡猾，像这样：

WITH
CTE
AS
(
    SELECT
        Info.PersonId AS ID1, People.PersonId AS ID2
    FROM
        Info
        INNER JOIN People ON Info.PersonId = People.PersonId
)
DELETE FROM CTE
WHERE ID1 = 1;

你会得到一个错误：

View or function 'CTE' is not updatable because the modification affects multiple base tables.

或者像这样：

WITH
CTE
AS
(
    SELECT
    PersonId
    FROM Info

    UNION ALL

    SELECT
    PersonId
    FROM People
)
DELETE FROM CTE
WHERE PersonId = 1;

你会得到另一个错误：

View 'CTE' is not updatable because the definition contains a UNION operator.

我可以在一个语句中删除两个表中的条目吗？

Can I delete entries from two tables in one statement?

sql

sql-server

sql-server-2012

人

信息