表名两端的引号究竟是做什么的? [英] What exactly do quotation marks around the table name do?

问题描述

我认为引号()只是分组标记的一种，但是我正在调试一些NHibernate代码，并注意到，虽然

I thought that the quotation mark (") was simply a type of grouping marker but I'm debugging some NHibernate code and notice that while

SELECT * FROM site WHERE site_id = 3;

工作正常

SELECT * FROM "site" WHERE site_id = 3;

表或视图失败不存在错误.

fails with a table or view does not exist error.

有什么作用?

推荐答案

在Oracle中将双引号引起来会使Oracle将标识符视为区分大小写，而不是使用不区分大小写的默认值.如果创建的表(或列)的名称周围带有双引号，则必须始终使用双引号引用标识符，并正确指定大小写(所有大写标识符除外，其中双引号无意义) ).

Putting double-quotes around an identifier in Oracle causes Oracle to treat the identifier as case sensitive rather than using the default of case-insensitivity. If you create a table (or a column) with double-quotes around the name, you must always refer to the identifier with double quotes and by correctly specifying the case (with the exception of all upper case identifiers, where double-quotes are meaningless).

在幕后，Oracle始终在进行区分大小写的标识符匹配.但是，在进行匹配之前，它始终将未用双引号引起来的标识符强制转换为大写.如果在标识符两边加上双引号，则Oracle会跳过对大写字母的强制转换.

Under the covers, Oracle is always doing case-sensitive identifier matching. But it always casts identifiers that are not double-quoted to upper case before doing the matching. If you put double-quotes around an identifier, Oracle skips the casting to upper case.

所以，如果您做类似的事情

So if you do something like

CREATE TABLE my_table( 
  col1 number,
  col2 number
)

可以

SELECT * FROM my_table
SELECT * FROM MY_TABLE
SELECT * FROM My_Table
SELECT * FROM "MY_TABLE"

但类似

SELECT * FROM "my_table" 

将失败.

另一方面，如果您做类似的事情

On the other hand, if you do something like

CREATE TABLE "my_other_table"( 
  col1 number,
  col2 number
)

你不能做

SELECT * FROM my_other_table
SELECT * FROM MY_OTHER_TABLE
SELECT * FROM My_Other_Table
SELECT * FROM "MY_OTHER_TABLE"

但是这个

SELECT * FROM "my_other_table" 

将起作用

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