在SQL语法中，如果您打算使用“在哪里”，“删除自”中的“来自”是否是可选的？ [英] In SQL syntax, is 'from' in 'delete from' optional if you plan to use 'where'?

问题描述

我是SQL新手。我们有一些适用于SQL Server 2005/2008，Oracle 10和Sybase的代码。

I am new to SQL. We have some code that should work on SQL Server 2005/2008, Oracle 10 as well as Sybase.

我正在编写一个脚本，试图找出给定的表存储过程会修改（但不会删除），例如插入，更新和删除。

I was writing a script to try to figure out which tables a given stored procedure modifies (but does not drop), e.g insert, update and delete.

一个被删除的 令人费解-有时我会看到类似这样的语句：

The delete one turned out being puzzling - sometimes I see statements like:

delete phone_book where ... 

相对于：

delete from phone_book where ...

那么...在这种情况下， from 关键字是真的可选吗？这会引起任何问题吗？

So ... is the from keyword truly optional in this case? Does this cause any problems? Is it just a bad style, or does it not matter?

我没有找到对 T-SQL ，这将使 from 是可选的。我想这将统一我上面提到的所有3个供应商。

I have not found a reference to T-SQL that would make from optional. I suppose that this is what would unify all 3 vendors I mentioned above.

欢迎问题/评论/链接（还是欢迎？）。

Questions/comments/links are welcomed (or is it welcome?).

推荐答案

在此位置 FROM 是可选的（ SQL Server ， Oracle ， Sybase ）。

At this place the FROM is optional (SQL Server, Oracle, Sybase).

但是，两者之间存在细微的差异：例如，Oracle允许为表名分配别名，而SQL Server则不允许。

However, there are subtle differences: Oracle for instance allows assigning an alias to the table name, where SQL Server doesn't; and other things are also a little bit different.

还要注意，您的 FROM 示例与以下示例不同：它是强制性的：

Also note that your FROM sample is differnet from the following where it is mandatory:

DELETE phone_book FROM some_table WHERE ...

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