如何在SAP HANA图中创建多个顶点

Question

我正在尝试在SAP HANA中创建2个（多个）顶点，例如-

为顶点ITEM和DATASET创建两个表

CREATE COLUMN TABLE "GREEK_MYTHOLOGY"."ITEM" (
"ITEM_ID" VARCHAR(100) PRIMARY KEY,
"ITEM_NAME" VARCHAR(100)
);

CREATE COLUMN TABLE "GREEK_MYTHOLOGY"."DATASET" (
"DATASET_ID" VARCHAR(100) PRIMARY KEY,
"DATASET_NAME" VARCHAR(100)
);

并创建边缘作为参考

CREATE COLUMN TABLE "GREEK_MYTHOLOGY"."REFERENCES" (
"REF_ID" INT UNIQUE NOT NULL,
"SOURCE" VARCHAR(100) NOT NULL
REFERENCES "GREEK_MYTHOLOGY"."ITEM" ("ITEM_ID")
ON UPDATE CASCADE ON DELETE CASCADE,
"TARGET" VARCHAR(100) NOT NULL
REFERENCES "GREEK_MYTHOLOGY"."DATASET" ("DATASET_ID")
ON UPDATE CASCADE ON DELETE CASCADE,
"TYPE" VARCHAR(100)
);

现在我想将两个顶点（ ITEM和DATASET ）都与如下边参考连接

CREATE GRAPH WORKSPACE "GREEK_MYTHOLOGY"."GRAPH"
EDGE TABLE "GREEK_MYTHOLOGY"."DATASET"
SOURCE COLUMN "SOURCE" 
TARGET COLUMN "TARGET"
VERTEX TABLE "GREEK_MYTHOLOGY"."ITEM" KEY COLUMN "ITEM_ID"
VERTEX TABLE "GREEK_MYTHOLOGY"."DATASET"KEY COLUMN "DATASET_ID"
KEY COLUMN "REF_ID";

但是它会抛出异常

VERTEX TABLE“ GREEK_MYTHOLOGY”。“ DATASET”关键列“ DATASET_ID”

sql syntax error: incorrect syntax near "VERTEX": line 6 col 1 (at pos 200)

是否可以在SAP HANA图中创建多个顶点？ 如果是，那么正确的方法是这样做。

Answer 1

这里有一个误会。 CREATE TABLE语句中的REFERENCES子句与您要表示的图形结构无关。 相反，它在两个表之间定义了外键约束 。

CREATE GRAPH WORKSPACE命令仅接受一个EDGE TABLE和一个VERTEX TABLE作为参数。 但是，您也可以在此处传递同义词或视图 。

这样，您可以创建一个视图"ALL_ITEMS"如下所示：

CREATE VIEW "GREEK_MYTHOLOGY"."ALL_ITEMS" as
  SELECT "ITEM_ID" as "ID", "ITEM_NAME" as "NAME"  FROM "GREEK_MYTHOLOGY"."ITEM"
  UNION 
  SELECT "DATASET_ID" as "ID", "DATASET_NAME" as "NAME" FROM "GREEK_MYTHOLOGY"."DATASET";

然后引用此视图：

CREATE GRAPH WORKSPACE "GREEK_MYTHOLOGY"."GRAPH"
       EDGE TABLE "GREEK_MYTHOLOGY"."DATASET"
            SOURCE COLUMN "SOURCE" 
            TARGET COLUMN "TARGET"
       VERTEX TABLE "GREEK_MYTHOLOGY"."ALL_ITEMS"
            KEY COLUMN "NAME";

可以使用这种方法，但是现在您必须确保"NAME"值在两个表中都是唯一的而不是NULL 。