UNION前INNER JOIN

Question

爲什麼當我INNER之前使用UNION JOIN這樣

select some_table1.some_column1, 
      some_table1.some_column2 
    FROM some_table1 
    UNION ALL 
    select some_table2.some_column1, 
      some_table2.some_column2 
    FROM some_table2 
    INNER JOIN some_table3 
    ON some_table3.some_column1 = some_table1.some_column1 

我有一個eror：無法綁定多個部分組成的識別碼 「some_table3.some_column1」？ 所有數據類型都是兼容的。

Answer 1

您正在收到錯誤，因爲這不是有效的SQL語法。 UNION ALL語法是：

SELECT <column1> 
FROM <table1> 
UNION ALL 
SELECT <column1> 
FROM <table2> 

像你正在嘗試做你不能從任何查詢引用列。如果你想參考，那麼你會想要使用這樣的事情：

select * 
from 
(
    select some_table1.some_column1, some_table1.some_column2 
    FROM some_table1 
    UNION ALL 
    select some_table2.some_column1, some_table2.some_column2 
    FROM some_table2 
) t1 
INNER JOIN some_table3 
ON some_table3.some_column1 = t1.some_column1 

Answer 2

你試圖加入some_table1到some_table3當some_table1不存在於查詢的後半部分時，只有第一個。

Answer 3

我猜你是想要這樣的事情？

SELECT 
(
     select some_table1.some_column1, 
       some_table2.some_column2 
     FROM some_table1 
     UNION ALL 
     select some_table2.some_column1, 
       some_table2.some_column2 
     FROM some_table2 
) sub 
     INNER JOIN some_table3 
     ON some_table3.some_column1 = sub.some_column1