將 2 個 CTE 替換為 1 個

Question

我在 postgresql 上有以下代碼：

    WITH CTE1 AS
(
SELECT
               value_1
              ,position
              ,value_3
              ,value_4
              ,value_5
From tabl_1
WHERE position = 1 
)

WITH CTE2 AS
(
SELECT
               value_1
              ,position
              ,value_3
              ,value_4
              ,value_5
From tabl_1
WHERE position = 2 
)   

INSERT INTO tbl_2
SELECT
CTE1.value_2 = IP_1
CTE2.value_2 = IP_2

FROM table_3 er
                LEFT JOIN CTE1 ON CTE1.value_1 = er.value_1 AND CTE1.value_3 = er.value_3
                LEFT JOIN CTE2 ON CTE2.value_1 = er.value_1 AND CTE2.value_3 = er.value_3

我在單獨的 CTE 中計算 IP_1、IP-2 的值，但我不知道如何將 2 個 CTE 替換為一個？ 或者其他方式。

Answer 1

復制你的代碼，它似乎有很多錯誤：

• 插入的兩列之間沒有逗號；
• value_2 不在您的任何一個 CTE 中。

這可以重構以刪除所有 CTE：

INSERT INTO 
    tbl_2
SELECT
    t1.value_2 = IP_1
    t2.value_2 = IP_2
FROM 
    table_3 er
    LEFT JOIN tabl_1 t1 ON t1.value_1 = er.value_1 AND t1.value_3 = er.value_3 AND t1.position = 1
    LEFT JOIN tabl_1 t2 ON t2.value_1 = er.value_1 AND t2.value_3 = er.value_3 AND t2.position = 2