我正在使用DB2LUW 11.5。我构建了一个json，并得到了如下输出

{
        "ID": 1,
        "NAME": "a",
        "B_OBJECTS": [{
                "ID": 1,
                "SIZE": 10
            }, {
                "ID": 1,
                "SIZE": 20
            }
        ]
    }

但是我希望B_OBJECTS的id只列出一次。

{
        "ID": 1,
        "NAME": "a",
        "B_OBJECTS": [{
                "ID": 1,
                "SIZE": 10
            }
        ]
    }

这是我的疑问...

WITH TABLE_A(ID,NAME) AS (
        VALUES (1, 'a')),
TABLE_B(ID, ID_A, SIZE) AS (
        VALUES (1, 1, 10), (1, 1, 20)),
JSON_STEP_1 AS (
        SELECT A.ID AS A_ID, A.NAME AS A_NAME, B.ID AS B_ID,
        JSON_OBJECT('ID' VALUE B.ID, 'SIZE' VALUE B.SIZE) B_JSON
        FROM TABLE_A A
        JOIN TABLE_B B ON B.ID_A = A.ID       
        GROUP BY A.ID, A.NAME, B.ID, B.SIZE),
JSON_STEP_2 AS (
 SELECT JSON_OBJECT ('ID' VALUE A_ID,
                     'NAME' VALUE A_NAME,
                     'B_OBJECTS' VALUE JSON_ARRAY (LISTAGG(B_JSON, ', ') WITHIN GROUP (ORDER BY B_ID) FORMAT JSON) FORMAT JSON
                    ) JSON_OBJS
 FROM JSON_STEP_1
 GROUP BY A_ID, A_NAME
) 
SELECT JSON_ARRAY (SELECT JSON_OBJS FROM JSON_STEP_2 FORMAT JSON) FROM SYSIBM.SYSDUMMY1;

我刚刚用附加表TABLE_C更新了查询

WITH 
  TABLE_A(ID,NAME) AS 
(
        VALUES (1, 'a')
)
, TABLE_B(ID, ID_A, SIZE) AS 
(
        VALUES (1, 1, 10), (1, 1, 20), (2, 1, 10), (2, 1, 20)
), TABLE_C(ID, ID_A, SIZE) AS
(
        VALUES (1, 1, 5), (2,1,10), (3,1,15)
)
, JSON_STEP_1 AS 
(
  SELECT A_ID, A_NAME, B_ID
  , JSON_OBJECT('ID' VALUE B_ID, 'SIZE' VALUE B_SIZE) B_JSON
  , JSON_OBJECT('ID' VALUE C_ID, 'SIZE' VALUE C_SIZE) C_JSON
  FROM
  (
        SELECT 
          A.ID AS A_ID, A.NAME AS A_NAME, B.ID AS B_ID, B.SIZE AS B_SIZE, C.ID AS C_ID, C.SIZE AS C_SIZE
        , ROW_NUMBER () OVER (PARTITION BY B.ID, B.ID_A, B.SIZE) AS RN_
        , ROW_NUMBER () OVER (PARTITION BY C.ID, C.ID_A, C.SIZE) AS RN1_
        
        FROM TABLE_A A
        JOIN TABLE_B B ON B.ID_A = A.ID      
        JOIN TABLE_C C ON C.ID_A = A.ID     
   )     
   WHERE RN_ = 1 AND RN1_ = 1
   GROUP BY A_ID, A_NAME, B_ID, B_SIZE, B_ID, B_SIZE, C_ID, C_SIZE
)
, JSON_STEP_2 AS 
(
 SELECT 
 JSON_OBJECT 
  (
    'ID' VALUE A_ID,
    'NAME' VALUE A_NAME,
    'B_OBJECTS' VALUE JSON_ARRAY (LISTAGG(B_JSON, ', ') WITHIN GROUP (ORDER BY B_ID) FORMAT JSON) FORMAT JSON,
    'C_OBJECTS' VALUE JSON_ARRAY (LISTAGG(C_JSON, ', ') WITHIN GROUP (ORDER BY B_ID) FORMAT JSON) FORMAT JSON
  ) JSON_OBJS
 FROM JSON_STEP_1
 GROUP BY A_ID, A_NAME
) 
SELECT JSON_ARRAY (SELECT JSON_OBJS FROM JSON_STEP_2 FORMAT JSON) FROM SYSIBM.SYSDUMMY1

输出应如下所示

{
        "ID": 1,
        "NAME": "a",
        "B_OBJECTS": [{
                "ID": 1,
                "SIZE": 10
            },
            {
                "ID": 1,
                "SIZE": 20
            },
            {
                "ID": 2,
                "SIZE": 10
            },
            {
                "ID": 2,
                "SIZE": 20
            }
        ],
        "C_OBJECTS": [{
                "ID": 1,
                "SIZE": 5
            },
            {
                "ID": 2,
                "SIZE": 10
            },
            {
                "ID": 3,
                "SIZE": 15
            }
        ]
    }