函数 PARSENAME() 是否与 QUOTENAME() 相反

Question

在问题MS-SQL 上是否有任何（隐藏的）内置函数来取消引用对象名称？作者正在寻求有关是否存在“取消引用”引用字符串的内部函数的建议。作者McNets已经注意到，一些内部函数可以处理引用（例如[MyTable]）和未引用（例如）MyTable传递的参数值（例如OBJECT_ID()）。

在David Browne - Microsoft给出的答案 ( 1 ) 中，引述如下：

... QUOTENAME 的反面是 PARSENAME，它具有导航多部分名称的附加功能。

我不同意这部分答案的以下评论：

我不同意，你可以修改传递给一个参数PARSENAME()来显示多部分的部分标识是它的SERVER，DATABASE，SCHEMA或OBJECT部分。但恕我直言，PARSENAME与此相反的说法QUOTENAME有点牵强。

我现在的问题是：

函数PARSENAME()是相反的QUOTENAME()吗？

Answer 1

根据ypercube的评论？？内容如下：

......你可以找到一个字符串，x这parsename(quotename(x),1)会比不同x？如果不是，则属于“反函数”的定义；) ...

...我创建了一个简单的语句来查看这些函数返回的不同值。代码如下：

代码

DECLARE 
-- Text that I will be converting using QUOTENAME()
@Text2Quote_1 AS NVARCHAR(20),
@Text2Quote_2 AS NVARCHAR(20),
@Text2Quote_3 AS NVARCHAR(20),
@Text2Quote_4 AS NVARCHAR(20),
-- The characters used for "quotation"
@QuoteChar_1 AS NCHAR(1),
@QuoteChar_2 AS NCHAR(1),
@QuoteChar_3 AS NCHAR(1),
-- The Parsing option as defined in the original MS documnenation for PARSSENAME()
@ParseParam AS INT

SET @Text2Quote_1 = N'Test'
SET @Text2Quote_2 = N'[Test]'
SET @Text2Quote_3 = N'Test.dbo.test'
SET @Text2Quote_4 = N'[Test].[dbo].[test]'

SET @QuoteChar_1 = ''''
SET @QuoteChar_2 = '[' 
SET @QuoteChar_3 = '"' 

SET @ParseParam = 1 -- Parsing level : Object name
-- checking the results for ' single quotes
SELECT  @Text2Quote_1 AS OriginalText_1,
        @Text2Quote_2 AS OriginalText_2,
        @Text2Quote_3 AS OriginalText_3,
        @Text2Quote_4 AS OriginalText_4
SELECT  QUOTENAME(@Text2Quote_1,@QuoteChar_1) AS QuotedText_1, 
        QUOTENAME(@Text2Quote_2,@QuoteChar_1) AS QuotedText_2, 
        QUOTENAME(@Text2Quote_3,@QuoteChar_1) AS QuotedText_3, 
        QUOTENAME(@Text2Quote_4,@QuoteChar_1) AS QuotedText_4
select  PARSENAME(QUOTENAME(@Text2Quote_1,@QuoteChar_1),@ParseParam) AS Parsed_QuotedText_1, 
        PARSENAME(QUOTENAME(@Text2Quote_2,@QuoteChar_1),@ParseParam) AS Parsed_QuotedText_2,
        PARSENAME(QUOTENAME(@Text2Quote_3,@QuoteChar_1),@ParseParam) AS Parsed_QuotedText_3,
        PARSENAME(QUOTENAME(@Text2Quote_4,@QuoteChar_1),@ParseParam) AS Parsed_QuotedText_4

基本上，我设置一个字符串值，输出该值，QUOTENAME()然后输出该值，然后PARSENAME()是QUOTENAME()ed 值并输出它。

结果

结果非常有趣：

OriginalText_1           OriginalText_2           OriginalText_3           OriginalText_4          
------------------------ ------------------------ ------------------------ ------------------------
Test                     [Test]                   Test.dbo.test            [Test].[dbo].[test]     

(1 row(s) affected)                                                                                

QuotedText_1             QuotedText_2             QuotedText_3             QuotedText_4            
------------------------ ------------------------ ------------------------ ------------------------
'Test'                   '[Test]'                 'Test.dbo.test'          '[Test].[dbo].[test]'   

(1 row(s) affected)                                                                                

Parsed_QuotedText_1      Parsed_QuotedText_2      Parsed_QuotedText_3      Parsed_QuotedText_4     
------------------------ ------------------------ ------------------------ ------------------------
'Test'                   NULL                     test'                    NULL                    

(1 row(s) affected)                                                                                

当基本文本Test.dbo.test( OriginalText_3 ) 传递给QUOTENAME()函数时，它会转换为：'Test.dbo.test'( QuotedText_3 )

当QuotedText_3串'Test.dbo.test'上，以传递PARSENAME()函数它被转换成：test'（Parsed_QuotedText_3）

结论

看来我已经证明了超立方体？？的论文是错误的，我认为可以安全地声明该函数PARSENAME()不是 的逆函数QUOTENAME()。

基于Aaron Bertrand在这里的反馈方括号的代码[ ]（添加到原始脚本）

方括号的附加代码 [ ]

-- checking the results for [ brackets                                                                           
SELECT  @Text2Quote_1 AS OriginalText_1,                                                                         
        @Text2Quote_2 AS OriginalText_2,                                                                         
        @Text2Quote_3 AS OriginalText_3,                                                                         
        @Text2Quote_4 AS OriginalText_4                                                                          
SELECT  QUOTENAME(@Text2Quote_1,@QuoteChar_2) AS QuotedText_1,                             
        QUOTENAME(@Text2Quote_2,@QuoteChar_2) AS QuotedText_2,                             
        QUOTENAME(@Text2Quote_3,@QuoteChar_2) AS QuotedText_3,                             
        QUOTENAME(@Text2Quote_4,@QuoteChar_2) AS QuotedText_4                              
select  PARSENAME(QUOTENAME(@Text2Quote_1,@QuoteChar_2),@ParseParam) AS Parsed_QuotedText_1,
        PARSENAME(QUOTENAME(@Text2Quote_2,@QuoteChar_2),@ParseParam) AS Parsed_QuotedText_2,
        PARSENAME(QUOTENAME(@Text2Quote_3,@QuoteChar_2),@ParseParam) AS Parsed_QuotedText_3,
        PARSENAME(QUOTENAME(@Text2Quote_4,@QuoteChar_2),@ParseParam) AS Parsed_QuotedText_4

方括号的输出 [ ]

OriginalText_1           OriginalText_2           OriginalText_3           OriginalText_4
------------------------ ------------------------ ------------------------ ------------------------
Test                     [Test]                   Test.dbo.test            [Test].[dbo].[test]

(1 row(s) affected)

QuotedText_1             QuotedText_2             QuotedText_3             QuotedText_4
------------------------ ------------------------ ------------------------ ------------------------
[Test]                   [[Test]]]                [Test.dbo.test]          [[Test]].[dbo]].[test]]]

(1 row(s) affected)

Parsed_QuotedText_1      Parsed_QuotedText_2      Parsed_QuotedText_3      Parsed_QuotedText_4
------------------------ ------------------------ ------------------------ ------------------------
Test                     [Test]                   Test.dbo.test            [Test].[dbo].[test]

(1 row(s) affected)

并完成双引号的代码

双引号的附加代码 "

-- checking the results for [ brackets                                                                           
SELECT  @Text2Quote_1 AS OriginalText_1,                                                                         
        @Text2Quote_2 AS OriginalText_2,                                                                         
        @Text2Quote_3 AS OriginalText_3,                                                                         
        @Text2Quote_4 AS OriginalText_4                                                                          
SELECT  QUOTENAME(@Text2Quote_1,@QuoteChar_3) AS QuotedText_1,                             
        QUOTENAME(@Text2Quote_2,@QuoteChar_3) AS QuotedText_2,                             
        QUOTENAME(@Text2Quote_3,@QuoteChar_3) AS QuotedText_3,                             
        QUOTENAME(@Text2Quote_4,@QuoteChar_3) AS QuotedText_4                              
select  PARSENAME(QUOTENAME(@Text2Quote_1,@QuoteChar_3),@ParseParam) AS Parsed_QuotedText_1,
        PARSENAME(QUOTENAME(@Text2Quote_2,@QuoteChar_3),@ParseParam) AS Parsed_QuotedText_2,
        PARSENAME(QUOTENAME(@Text2Quote_3,@QuoteChar_3),@ParseParam) AS Parsed_QuotedText_3,
        PARSENAME(QUOTENAME(@Text2Quote_4,@QuoteChar_3),@ParseParam) AS Parsed_QuotedText_4

双引号的输出 "

OriginalText_1           OriginalText_2           OriginalText_3           OriginalText_4
------------------------ ------------------------ ------------------------ ------------------------
Test                     [Test]                   Test.dbo.test            [Test].[dbo].[test]

(1 row(s) affected)

QuotedText_1             QuotedText_2             QuotedText_3             QuotedText_4
------------------------ ------------------------ ------------------------ ------------------------
"Test"                   "[Test]"                 "Test.dbo.test"          "[Test].[dbo].[test]"

(1 row(s) affected)

Parsed_QuotedText_1      Parsed_QuotedText_2      Parsed_QuotedText_3      Parsed_QuotedText_4
------------------------ ------------------------ ------------------------ ------------------------
Test                     [Test]                   Test.dbo.test            [Test].[dbo].[test]

(1 row(s) affected)

根据ypercube™的反馈和Aaron Bertrand的新反馈，我们得出了共同的结论

PARSENAME()是QUOTENAME()如果满足以下条件的倒数：

PARSENAME(x,1)-1(QUOTENAME(x,q))哪里q={1,2}和x='{'any_string_value'}

参考：

• PARSENAME (Transact SQL) (Microsoft Docs)
• QUOTENAME (Transact SQL) (Microsoft Docs)