代码

SELECT
c.GroupedField1,
IS_DEFINED(c.GroupedField2) ? c.GroupedField2 : null  as GroupedField2,
COUNT(1) AS GroupCount
FROM
c
GROUP  BY
c.GroupedField1,
IS_DEFINED(c.GroupedField2) ? c.GroupedField2 : null

该查询将c容器中的文档按GroupedField1和GroupedField2分组，并计算每个组中的文档数。如果缺少GroupedField2或null，则在分组时将其替换为null。
尝试此代码与样本输入和下面是结果。输入

{
    "id": "1",
    "GroupedField1": "A",
    "GroupedField2": "X"
},
{
    "id": "2",
    "GroupedField1": "A",
    "GroupedField2": "Y"
},
{
    "id": "3",
    "GroupedField1": "B",
    "GroupedField2": null
},
{
    "id": "4",
    "GroupedField1": "B"
}

输出：

[
    {
        "GroupedField1": "B",
        "GroupedField2": null,
        "GroupCount": 2
    },
    {
        "GroupedField1": "A",
        "GroupedField2": "Y",
        "GroupCount": 1
    },
    {
        "GroupedField1": "A",
        "GroupedField2": "X",
        "GroupCount": 1
    }
]