[英]SQL transform JSON: select one field from json array objects
I have table created with a script我有一个用脚本创建的表
CREATE TABLE [dbo].[Queries]
(
[Id] [INT] NOT NULL,
[Name] [NVARCHAR](MAX) NOT NULL,
[Module] [NCHAR](64) NOT NULL,
[Query] [NVARCHAR](MAX) NOT NULL,
PRIMARY KEY (Id)
)
GO
where Query
column is JSON string like:其中Query
列是 JSON 字符串,如:
[
{
"FieldName": "TargetFieldName",
"Filters": [
{ /* Description Filter 1 */ },
...
{ /* Description Filter N */ }
]
}
]
And I'd like to select from that table: Id, Name, and distinct list of column names as json array in THIRD column.我想从该表中选择:Id、Name和列名的不同列表作为第三列中的json 数组。
For example for row:例如对于行:
-------------------------------------------------------------------------------------------------
| Id | Name | Query |
-------------------------------------------------------------------------------------------------
| 7 | Query 7 | [{"FieldName": "A", ... },{ "FieldName": "B" ...},{"FieldName": "B", ... }] |
-------------------------------------------------------------------------------------------------
I'd like to get我想得到
| Id | Name | DistinctFieldNames |
+----+---------+--------------------+
| 7 | Query 7 | ["A","B"] |
My questions are:我的问题是:
Seems like the easiest would be to use a subquery to read the JSON, and the STRING_AGG
to create the new one:似乎最简单的方法是使用子查询来读取 JSON,并使用STRING_AGG
来创建新的:
SELECT V.ID,
V.Name,
'[' + STRING_AGG('"' + ca.FieldName + '"',',') WITHIN GROUP (ORDER BY ca.FieldName) + ']'
FROM (VALUES(7,'Query 7','[{"FieldName": "A"},{ "FieldName": "B"},{"FieldName": "B"}]'))V(ID,[Name], Query)
CROSS APPLY (SELECT DISTINCT OJ.FieldName
FROM OPENJSON (V.Query)
WITH (FieldName char(1)) OJ) ca --May need larger size, char(1) based on your sample data
GROUP BY V.ID,
V.[Name];
You should know that this code only run on SQL Server 2017 and higher version.您应该知道此代码仅在 SQL Server 2017 及更高版本上运行。
SELECT Id,Name,
(SELECT STRING_AGG(JSON_VALUE(value, '$.FieldName'), ',') As FieldName
FROM OPENJSON(Queries.Query))
FROM dbo.Queries
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