Question

我一直在使用Substring，左，右，charindex并不能完全起作用

如果这是列名'Data'中的值（全部为一行）

{"email":{"RecipientId":"usertest","RecipientEmail":"test@test.com","Subject":"This is a test subject heading","RecipientSubject":"A recipient subject"}}

如何执行SELECT语句来查找'Subject'标题，然后获取“ This is a test subject”数据？每条记录的Subject值都不同，所以我根本找不到“ This is a test subject”。

所以最终结果应该是这是SELECT结果的测试对象

Answer 1

以下查询应执行您想要的操作：

declare @string varchar(max);
set @string = '{"email":{"RecipientId":"usertest","RecipientEmail":"test@test.com","Subject":"This is a test subject heading","RecipientSubject":"A recipient subject"}}';

select substring(@string,charindex('"Subject":',@string)+11,charindex('"RecipientSubject"',@string)-charindex('"Subject"',@string)-13);

Answer 2

简单而俗气的方法是这样的：

SELECT SUBSTRING(
                 t.YourString
                ,A.StartPosition
                ,CHARINDEX('"'
                          ,t.YourString
                          ,A.StartPosition+1) - A.StartPosition
                 )
FROM @dummyTable t
CROSS APPLY(SELECT CHARINDEX('"Subject":"',t.YourString)+11) A(StartPosition)

我使用APPLY来计算值并像使用变量一样使用它。这个想法是：找到起点，然后从那里寻找结束语。但是，只要内容包含（转义的）引号（如

"Subject":"This is \"quoted\" internally"

更通用的方法

从v2016 JSON支持开始。使用这个（或更高版本）的版本，这真的很简单：

使用此原型表进行测试

DECLARE @dummyTable TABLE (YourString VARCHAR(1000));
INSERT INTO @dummyTable VALUES('{"email":{"RecipientId":"usertest","RecipientEmail":"test@test.com","Subject":"This is a test subject heading","RecipientSubject":"A recipient subject"}}');

-OPENJSON方法将为您阅读：

SELECT JsonContent.*
FROM @dummyTable t
CROSS APPLY OPENJSON(t.YourString,'$.email') 
WITH(RecipientId VARCHAR(100)
    ,RecipientEmail VARCHAR(100)
    ,[Subject] VARCHAR(100)
    ,RecipientSubject VARCHAR(100)) JsonContent;

但是使用较低的版本，您将需要欺骗它。将JSON转换为以属性为中心的XML 最为简单，如下所示：

<email RecipientId="usertest" RecipientEmail="test@test.com" Subject="This is a test subject heading" RecipientSubject="A recipient subject" />

我们可以通过一些字符串方法来实现这一点，我必须警告您，存在一些禁止使用字符和其他东西的陷阱...尝试一下：

SELECT Casted.ToXml.value('(/email/@RecipientId)[1]','varchar(1000)') AS RecipientId
      ,Casted.ToXml.value('(/email/@RecipientEmail)[1]','varchar(1000)') AS RecipientEmail
      ,Casted.ToXml.value('(/email/@Subject)[1]','varchar(1000)') AS [Subject]
      ,Casted.ToXml.value('(/email/@RecipientSubject)[1]','varchar(1000)') AS RecipientSubject
      ,Casted.ToXml.query('.') LookHowThisWasTransformed
FROM @dummyTable t 
CROSS APPLY
(
    SELECT CAST(CONCAT('<email '
                      ,REPLACE(REPLACE(REPLACE(REPLACE(t.YourString,'{"email":{"',''),'}}',''),'","','" '),'":"',' ="')
                      ,' />') AS XML)
) Casted(ToXml);

找到其他子串后提取子串

2 个答案: