Snowflake使用CTE创建表

Question

Snowflake 是否允许您创建一系列 CTE，然后最后将它们连接在一起以创建表格？

例如：

with CTE1 as ( SELECT * FROM TABLE1)
,CTE2 AS (SELECT * FROM TABLE2)
,CTE3 AS (SELECT * FROM TABLE3)

CREATE TABLE TABLE_NAME_HERE AS 
SELECT * FROM CTE1 AS 1
LEFT JOIN CTE2 AS 2 ON 1.KEY = 2.KEY
LEFT JOIN CTE3 AS 3 ON 1.KEY = 3.KEY

我收到unexpected 'CREATE'.错误

Answer 1

对的，这是可能的：

CREATE TABLE TABLE_NAME_HERE AS 
WITH CTE1 as ( SELECT * FROM TABLE1)
    ,CTE2 AS (SELECT * FROM TABLE2)
    ,CTE3 AS (SELECT * FROM TABLE3)
SELECT *     -- here should be explicit column list to avoid name duplication error
FROM CTE1 AS 1
LEFT JOIN CTE2 AS 2 ON 1.KEY = 2.KEY
LEFT JOIN CTE3 AS 3 ON 1.KEY = 3.KEY;

Answer 2

这是一个有趣的形式，因为 CTAS (CREATE TABLE AS) 形式是

CREATE TABLE <name> AS <select>

SELECT 形式可以有一个 CTE，CTE 形式是

WITH <name> AS <select>

CTE 也可以在子选择中，因为“它只是一个选择”，因此

SELECT <columns> 
FROM (
    WITH cte_1 AS (
         SELECT <columns>
         FROM table
    )
    SELECT <columns>
    FROM cte_1
)

这说明了为什么 Lukasz 显示的形式是正确的，因为如果我们添加更多括号

CREATE TABLE name AS (
    WITH cte_1 AS (
        SELECT <columns>
        FROM table
    )
    SELECT <columns>
    FROM cte_1
)