SQL 转换 JSON：从 json 数组对象中选择一个字段

似乎最简单的方法是使用子查询来读取 JSON，并创建新的： STRING_AGG

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];