如何从 SQL Server 中的 VARCHAR() 中删除尾随 CHAR(0)？答案

【问题标题】：How to remove trailing CHAR(0) from VARCHAR() in SQL Server?如何从 SQL Server 中的 VARCHAR() 中删除尾随 CHAR(0)？
【发布时间】：2014-01-22 12:08:23
【问题描述】：

在 Microsoft SQL Server 中，我尝试通过将 varbinary() 存储到上下文信息中来将 varchar() 字符串传递给触发器。

通过CONTEXT_INFO 传递数据本身不是问题。

我的问题是，我必须将 varchar() 转换为 varbinary() 才能将数据传递给上下文信息，并且转换回 varchar() 会产生一个尾随 CHAR(0) 字符，我可以不再妥善处理。

我试图找到CHAR(0) 的第一个索引以子串到一个新的正确字符串，但没有成功。其他内置函数也无法正确处理 CHAR(0) 字符。

但是：

LEN() => 总是返回 128，
CHARINDEX() => 找不到 CHAR(0)，
RTRIM() => 不修剪不可打印的 CHAR(0) 字符，
REPLACE() => 不能代替 CHAR(0)，

执行异常：

SELECT * FROM (SELECT (@textbin) AS [blabla]) AS [result] FOR XML

我特别需要传递的字符串，作为纯文本，没有尾随空格/CHAR(0) 将字符串放入 xml。

PS.: xml 中的 BINARY BASE64 表示不是我可以使用的选项！

这里是一个测试 SQL 脚本

DECLARE @text VARCHAR(128)
DECLARE @bintext BINARY(128)
DECLARE @textbin VARCHAR(128)

SET @text = 'test'
--SET @text = 'test' + CHAR(0)
--SET @text = 'test' + CHAR(0) + CHAR(1)
SET @bintext = CONVERT(BINARY(128), @text)
SET @textbin = CONVERT(VARCHAR(128), @bintext)

SET CONTEXT_INFO @bintext
SET @textbin = CAST(CONTEXT_INFO() AS VARCHAR(128))

SELECT
    @text AS [content], LEN(@text) AS [len], DATALENGTH(@text) AS [datalength]
    , REVERSE(@text) AS [reverse]
    , LEN(RTRIM(@text)) AS [len_rtrim]
    , CHARINDEX(CHAR(0), @text) AS [charindex]
    , (SELECT * FROM (SELECT @text AS [text]) AS [result] FOR XML AUTO, BINARY BASE64) AS [xml]
SELECT
    @bintext AS [content], LEN(@bintext) AS [len], DATALENGTH(@bintext) AS [datalength]
    , REVERSE(@bintext) AS [reverse]
    , CHARINDEX(CHAR(0), @bintext) AS [charindex]
    , (SELECT * FROM (SELECT @bintext AS [bintext]) AS [result] FOR XML AUTO, BINARY BASE64) AS [xml]
SELECT
    @textbin AS [content], LEN(@textbin) AS [len], DATALENGTH(@textbin) AS [datalength]
    , REVERSE(@textbin) AS [reverse]
    , LEN(LTRIM(@textbin)) AS [len_rtrim]
    , CHARINDEX(CHAR(0), @textbin) AS [charindex]
    , (SELECT * FROM (SELECT REPLACE(@textbin, CHAR(0), '?') AS [textbin]) AS [result] FOR XML AUTO, BINARY BASE64) AS [xml]

IF @textbin = @text
    SELECT '(@textbin = @text) => TRUE' AS [if]
ELSE
    SELECT '(@textbin = @text) => FALSE' AS [if]

IF @textbin = 'test'
    SELECT '(@textbin = ''test'') => TRUE' AS [if]
ELSE
    SELECT '(@textbin = ''test'') => FALSE' AS [if]

IF @textbin = 'test' + CHAR(0) + CHAR(1)
    SELECT '(@textbin = ''test'' + CHAR(0) + CHAR(1)) => TRUE' AS [if]
ELSE
    SELECT '(@textbin = ''test'' + CHAR(0) + CHAR(1)) => FALSE' AS [if]

IF @textbin LIKE 'test'
    SELECT '(@textbin LIKE ''test'') => TRUE' AS [if]
ELSE
    SELECT '(@textbin LIKE ''test'') => FALSE' AS [if]

IF @textbin LIKE 'test%'
    SELECT '(@textbin LIKE ''test%'') => TRUE' AS [if]
ELSE
    SELECT '(@textbin LIKE ''test%'') => FALSE' AS [if]

SELECT * FROM (SELECT (@textbin) AS [context_info]) AS [test] FOR XML AUTO, BINARY BASE64
-- SELECT * FROM (SELECT (@textbin) AS [context_info]) AS [test] FOR XML AUTO, TYPE, BINARY BASE64
-- SELECT * FROM (SELECT (@textbin) AS [context_info]) AS [test] FOR XML AUTO

-- relatet to "@textbin"
-- LEN() => returns always 128,
-- CHARINDEX() => does not find CHAR(0),
-- RTRIM() => does not trim non printable CHAR(0) chars,
-- REPLACE() => does not replace CHAR(0),
-- exception on executing: SELECT * FROM (SELECT (@textbin) AS [context_info]) AS [test] FOR XML AUTO, TYPE, BINARY BASE64
-- exception on executing: SELECT * FROM (SELECT (@textbin) AS [context_info]) AS [test] FOR XML AUTO

【问题讨论】：

尝试使用 DATALENGTH 获取字段长度
我觉得重复的可以看这里stackoverflow.com/q/2828333/1692632
如果您认为需要将数据传递给触发器，那么设计中就会发生一些非常奇怪的事情。您正在使用触发器，就好像它们是存储过程一样。
LEN 和 DATALENGTH 总是返回 128。我需要字符串本身的长度

标签： sql sql-server xml

【解决方案1】：

正如达卡所注意到的，

这是一个重复的问题： What is the Null Character literal in TSQL?

...谢谢你给我看。

此更改修复了我的代码：

SET @textbin = REPLACE(CAST(CAST(CONTEXT_INFO() AS VARCHAR(128)) COLLATE SQL_Latin1_General_CP1_CI_AS AS VARCHAR(128)), CHAR(0), '')

【讨论】：