• 集合操作 (UNION，INTERSECT， MINUS)
    • UNION，UNION DISTINCT，UNION ALL
      • 示例
    • INTERSECT
    • MINUS

    集合操作 (UNION，INTERSECT， MINUS)

    UNION，UNION DISTINCT，UNION ALL

    UNION DISTINCT (简称 UNION)返回数据集 A 和 B 的并集（不包含重复元素）。

    UNION ALL 返回数据集 A 和 B 的并集（包含重复元素）。UNION 语法为

    1. <left> UNION [DISTINCT | ALL] <right>

    <left> 和 <right> 必须列数相同，且数据类型相同。

    示例

    1. nebula> GO FROM 1 OVER e1 \
    2.         UNION \
    3.         GO FROM 2 OVER e1

    以上语句返回点 1 和 2 (沿边 e1) 关联的唯一的点。

    1. nebula> GO FROM 1 OVER e1 \
    2.         UNION ALL\
    3.         GO FROM 2 OVER e1

    以上语句返回点 1 和 2 关联的点，其中存在重复点。

    UNION 亦可与 YIELD 同时使用，例如以下语句：

    1. nebula> GO FROM 1 OVER e1 YIELD e1._dst AS id, e1.prop1 AS left_1, $$.tag.prop2 AS left_2 -- query 1
    2. ==========================
    3. | id  | left_1 | left_2  |
    4. ==========================
    5. | 104 |    1   |    2    |    -- line 1
    6. --------------------------
    7. | 215 |    4   |    3    |    -- line 3
    8. --------------------------
    10. nebula> GO FROM 2,3 OVER e1 YIELD e1._dst AS id, e1.prop1 AS right_1, $$.tag.prop2 AS right_2  -- query 2
    11. ===========================
    12. | id  | right_1 | right_2 |
    13. ===========================
    14. | 104 |    1    |    2    |    -- line 1
    15. ---------------------------
    16. | 104 |    2    |    2    |    -- line 2
    17. ---------------------------
    1. nebula> GO FROM 1 OVER e1 YIELD e1._dst AS id, e1.prop1 AS left_1, $$.tag.prop2 AS left_2
    2. UNION /* DISTINCT */
    3. GO FROM 2,3 OVER e1 YIELD e1._dst AS id, e1.prop1 AS right_1, $$.tag.prop2 AS right_2

    以上语句返回

    1. =========================
    2. | id  | left_1 | left_2 |    -- UNION or UNION DISTINCT. The column names come from query 1
    3. =========================
    4. | 104 |    1   |    2   |    -- line 1
    5. -------------------------
    6. | 104 |    2   |    2   |    -- line 2
    7. -------------------------
    8. | 215 |    4   |    3   |    -- line 3
    9. -------------------------

    请注意第一行与第二行返回相同 id 的点，但是返回的值不同。DISTINCT 检查返回结果中的重复值。所以第一行与第二行的返回结果不同。UNION ALL 返回结果为

    1. nebula> GO FROM 1 OVER e1 YIELD e1._dst AS id, e1.prop1 AS left_1, $$.tag.prop2 AS left_2   \
    2.         UNION ALL   \
    3.         GO FROM 2,3 OVER e1 YIELD e1._dst AS id, e1.prop1 AS right_1, $$.tag.prop2 AS right_2
    5. =========================
    6. | id  | left_1 | left_2 |    -- UNION ALL
    7. =========================
    8. | 104 |    1   |    2   |    -- line 1
    9. -------------------------
    10. | 104 |    1   |    2   |    -- line 1
    11. -------------------------
    12. | 104 |    2   |    2   |    -- line 2
    13. -------------------------
    14. | 215 |    4   |    3   |    -- line 3
    15. -------------------------

    INTERSECT

    INTERSECT 返回集合 A 和 B ( A ⋂ B)的交集。

    1. <left> INTERSECT <right>

    与 UNION 类似， <left> 和 <right> 必须列数相同，且数据类型相同。此外，只返回 <left> 右 <right> 相同的行。例如：

    1. nebula> GO FROM 1 OVER e1 YIELD e1._dst AS id, e1.prop1 AS left_1, $$.tag.prop2 AS left_2
    2. INTERSECT
    3. GO FROM 2,3 OVER e1 YIELD e1._dst AS id, e1.prop1 AS right_1, $$.tag.prop2 AS right_2

    返回

    1. =========================
    2. | id  | left_1 | left_2 |
    3. =========================
    4. | 104 |    1   |    2   |    -- line 1
    5. -------------------------

    MINUS

    返回 A - B 数据的差集，此处请注意运算顺序。例如：

    1. nebula> GO FROM 1 OVER e1 YIELD e1._dst AS id, e1.prop1 AS left_1, $$.tag.prop2 AS left_2
    2. MINUS
    3. GO FROM 2,3 OVER e1 YIELD e1._dst AS id, e1.prop1 AS right_1, $$.tag.prop2 AS right_2

    返回

    1. ==========================
    2. | id  | left_1 | left_2  |
    3. ==========================
    4. | 215 |    4   |    3    |     -- line 3
    5. --------------------------

    如果更改 MINUS 顺序

    1. nebula> GO FROM 2,3 OVER e1 YIELD e1._dst AS id, e1.prop1 AS right_1, $$.tag.prop2 AS right_2
    2. MINUS
    3. GO FROM 1 OVER e1 YIELD e1._dst AS id, e1.prop1 AS left_1, $$.tag.prop2 AS left_2

    则返回

    1. ===========================
    2. | id  | right_1 | right_2 |    -- column named from query 2
    3. ===========================
    4. | 104 |    2    |    2    |    -- line 2
    5. ---------------------------