如何将具有相同数据类型的两个不同列的结果放在一列中，以使两个表中的两行在目标表中都是唯一的

Question

例如我有两列：

Column A: dog, cat, mouse

Column B: truck, jeep, lorry

我想要一种情况：

Column C : dog, truck, cat, jeep, mouse, lorry

我正在使用雪花

Answer 1

假设 colA、colB 列是字符串，则应首先将值拆分为原子值 SPLIT_TO_TABLE 并再次组合 LISTAGG：

SELECT ID, COLA, COLB, LISTAGG(COL, ', ') AS colC
FROM (
  SELECT ID, COLA, COLB, TRIM(s1.VALUE::STRING) AS col
  FROM tab
  ,TABLE(SPLIT_TO_TABLE(tab.colA, ',')) AS s1
  UNION
  SELECT ID, COLA, COLB, TRIM(s2.VALUE::STRING) AS col
  FROM tab
  ,TABLE(SPLIT_TO_TABLE(tab.colB, ',')) AS s2
) AS sub
GROUP BY ID, COLA, COLB
ORDER BY ID;

对于样本数据：

CREATE OR REPLACE TABLE tab
AS
SELECT 1 AS id, 'dog, cat, mouse' AS colA, 'truck, jeep, lorry' AS colB UNION 
SELECT 2 AS id, 'sparrow' AS colA, 'sparrow, parrot' AS colB;

Output：

---

旁注：对于存储非原子值 ARRAY 是更好的选择：

CREATE OR REPLACE TABLE tab
AS
SELECT 1 AS id, ['dog', 'cat', 'mouse'] AS colA, ['truck', 'jeep', 'lorry'] AS colB UNION 
SELECT 2 AS id, ['sparrow'] AS colA, ['sparrow', 'parrot'] AS colB;

然后组合是使用ARRAY_UNION_AGG的问题：

SELECT ID, ARRAY_UNION_AGG(COL) AS COLC
FROM (
  SELECT ID, COLA AS col FROM tab
  UNION ALL
  SELECT ID, COLB AS col FROM tab
) sub
GROUP BY ID
ORDER BY ID;

Output：

Answer 2

考虑一个 UNION 查询：

SELECT 1 AS GrpID, FieldA AS Data FROM tablename
UNION SELECT 2, FieldB FROM tablename;