Sql Query获取json结果中没有列名的数组

Question

我有一个包含以下字段的表格

 Id     RequestId     CategoryId
 1      112           1
 2      123           1
 3      123           2

SELECT      R.RequestId,
            (SELECT RC.CategoryId FROM Request RC WHERE RC.Id = R.Id FOR JSON AUTO) AS Categories
FROM        Request R

上面的查询返回如下所述的数据

 RequestId     Categories
 112           [{"CategoryId":"1"}]
 123           [{"CategoryId":"1"},{"CategoryId":"2"}]

但是，我希望不应该为json数组中的每个项重复列名称CategoryId。因此，我的预期结果是：

 RequestId     Categories
 112           ["1"]
 123           ["1","2"]

Answer 1

用过：SQL to JSON - array of objects to array of values in SQL 2016

create table Request (
  Id int,
  RequestId int,
  CategoryId int
)
GO

insert into Request (Id,RequestId,CategoryId) values
( 1,      112,           1),
( 2,      123,           1),
( 3,      123,           2);
GO

SELECT distinct R.RequestId,
            (
SELECT  
  JSON_QUERY('[' + STUFF(( SELECT ',' + '"' + convert(varchar(10), RC.CategoryId) + '"' 
FROM Request RC
WHERE RC.RequestId = R.RequestId
FOR XML PATH('')),1,1,'') + ']' ) Categories  
FOR JSON PATH , WITHOUT_ARRAY_WRAPPER 
            ) AS Categories
FROM Request R
GO

RequestId | Categories              
--------: | :-----------------------
      112 | {"Categories":["1"]}    
      123 | {"Categories":["1","2"]}

SELECT  distinct R.RequestId,

JSON_QUERY(
            (
SELECT  
  JSON_QUERY('[' + STUFF(( SELECT ',' + '"' + convert(varchar(10), RC.CategoryId) + '"' 
FROM Request RC
WHERE RC.RequestId = R.RequestId
FOR XML PATH('')),1,1,'') + ']' ) Categories  
FOR JSON PATH , WITHOUT_ARRAY_WRAPPER 
            )
, '$.Categories' )
FROM Request R
GO

RequestId | (No column name)
--------: | :---------------
      112 | ["1"]           
      123 | ["1","2"]       

db <>小提琴here

Answer 2

可以使用REPLACE实现：

 declare @test table ([Id] int, [RequestId] int, [CategoryId] int)
 insert into @test values
   (1, 112, 1)
 , (2, 123, 1)
 , (3, 123, 2)

    SELECT      R.RequestId,
                json_query(replace(replace((SELECT RC.CategoryId FROM @test RC WHERE RC.Id = R.Id FOR JSON AUTO), '{"CategoryId":', '"'), '}','"'))  AS Categories
    FROM        @test R

Answer 3

据我所知，你需要自己聚合字符串，然后将其转换为json。例如，在Sql Server 2017中，您可以使用STRING_AGG：

select
    t.RequestId,
    concat('[',string_agg(t.CategoryId, ','),']') as Categories
from Table1 as t
group by
    t.RequestId

sql fiddle demo

如果您需要将数组值设置为字符串而不是整数，则可以手动添加"字符，并且您可能还需要使用STRING_ESCAPE以便安全地转换特殊字符：

select
    t.RequestId,
    concat('[',string_agg(concat('"', string_escape(t.CategoryId, 'json'),'"'),','),']') as Categories
from Table1 as t
group by
    t.RequestId

sql fiddle demo

在早期版本的Sql Server中，您可以使用xml技巧或创建自定义clr聚合。