是否有可能SQL查詢中設置一個標誌

Question

我試圖做這樣的

(SELECT ID, Name FROM Book) 
UNION 
(SELECT ID, Name FROM Author) 

一個SQL查詢，我想在最後的表就知道哪個ID是從書，哪些來自作者 設置一個標誌或類似的東西。

Answer 1

只需選擇一個靜態文本，如

(SELECT ID, Name, "Book" FROM Book) UNION (SELECT ID, Name, "Author" FROM Author) 

Answer 2

你可以這樣做：

SELECT ID, Name, 'From Book' AS FromWhome 
FROM Book 
UNION 
SELECT ID, Name, 'From Author' 
FROM Author 

Answer 3

選擇值允許列和表達式，你也可以命名新列結果是這樣的：

SELECT ID, Name, 'book' as tag FROM Book 
UNION 
SELECT ID, Name, 'author' as tag FROM Author