如何将几列从一列 table 插入到只有一列 unique/distinct 的另一列？

Question

我正在尝试创建星型模式，目前正在处理 table 维度。我想将几列从一列 table 复制到另一列，但同时我想让其中一列的结果值唯一。

这些是我正在使用的 table： DWH_PRICE_PAID_RECORDS

CREATE TABLE "DWH_PRICE_PAID_RECORDS" ("TRANSACTION_ID" VARCHAR(50) NOT NULL, "PRICE" INTEGER, "DATE_OF_TRANSFER" DATE NOT NULL, "PROPERTY_TYPE" CHAR(1), "OLD_NEW" CHAR(1), "DURATION" CHAR(1), "TOWN_CITY" VARCHAR(50), "DISTRICT" VARCHAR(50), "COUNTY" VARCHAR(50), "PPDCATEGORY_TYPE" CHAR(1), "RECORD_TYPE" CHAR(1));

 ALTER TABLE "DWH_PRICE_PAID_RECORDS" ADD CONSTRAINT "PK3" PRIMARY KEY ("TRANSACTION_ID");

和DIM_REGION

CREATE TABLE "DIM_REGION" ("REGION_ID" INTEGER generated always as identity (start with 1 increment by 1), "TRANSACTION_ID" VARCHAR(50), "TOWN" VARCHAR(50), "COUNTY" VARCHAR(50), "DISTRICT" VARCHAR(50), "LATITUDE" VARCHAR(50), "LONGITUDE" VARCHAR(50), "COUNTRY_STRING" VARCHAR(50));

ALTER TABLE "DIM_REGION" ADD CONSTRAINT "PK8" PRIMARY KEY ("REGION_ID");

我的第一次尝试是使用 "select distinct" 但这只会删除所有合并的列的所有重复项。我想要一个区域维度，"town" 应该是标识符，以匹配 DIM_REGION 与我稍后将在数据集市上创建的事实 table（称为 DM_PRICE_PAID_RECORDS） .

DWH_PRICE_PAID_RECORDS table 有大约 10k 条记录，但只有 938 个独特的城镇。我想将 dim_region 中的那 938 个城镇作为 ID 以及县、区等其他列

这是可行的，但当然其他一切都是 NULL，但城镇：

INSERT INTO DIM_REGION (TOWN) SELECT (town_city) from DWH_PRICE_PAID_RECORDS GROUP BY town_city;

所以我想我只需要添加额外的列

INSERT INTO DIM_REGION (TOWN, County, District) SELECT town_city, county, district from DWH_PRICE_PAID_RECORDS GROUP BY town_city;

但是当我这样做时，我收到了这条错误信息（错误信息是德语，抱歉，我不得不翻译）：

ERROR 42Y36 Column reference: "DWH_PRICE_PAID_RECORDS.COUNTY" is invalid or part of a invalid statement. When using SELECT and GROUP BY the selected columns and statements must be valid group- or aggregation expressions.

你能帮帮我吗？或者你有别的想法我还能怎样得到我想要的结果？

非常感谢！

Answer 1

你太接近了！

INSERT INTO DIM_REGION (TOWN, County, District) SELECT town_city, county, district from DWH_PRICE_PAID_RECORDS GROUP BY town_city, county, district;

这应该可以完成工作。使用分组依据时，SELECT 列表中不是聚合的所有内容都必须出现在 GROUP BY 子句中。

顺便说一句，TRANSACTION_ID真的属于table维度吗？

Answer 2

如果其他 2 列无关紧要，您可以这样做：

INSERT INTO DIM_REGION (TOWN, County, District) 
SELECT town_city, MAX(county), MAX(district) 
FROM DWH_PRICE_PAID_RECORDS 
GROUP BY town_city

这将使每个城镇只有 1 行。

如何将几列从一列 table 插入到只有一列 unique/distinct 的另一列？

How can I Insert several columns from one table to another having only 1 column unique/distinct?

sql

db2

derby