在使用MySQL創建的VIEW中看不到NULL值

Question

在MySQL中創建視圖時，我無法在創建的視圖中看到具有NULL值的行。

在這裏我們可以看到表mail_prijava

和表status

所以，我想用下面

CREATE OR REPLACE VIEW 
v_mail_prijava_test 
AS 
SELECT 
mail_prijava.id, 
mail_prijava.naselje AS naselje, 
mail_prijava.ulica AS ulica, 
mail_prijava.email AS email, 
mail_prijava.napomena AS napomena, 
IFNULL(status.opis AS "test") AS status 
DATE_FORMAT(datum_unosa, "%d.%m.%Y.") AS datum_servisa, 
vrijeme_unosa 
FROM mail_prijava 
INNER JOIN status ON status.id = mail_prijava.status_id 

SQL代碼來創建表 mail_prijava和表 status VIEW

當使用上面的代碼，我得到這個表：

問題是該行從表空值mail_prijava沒有顯示，我想知道這是爲什麼，是它可以顯示在創建視圖空行。

謝謝

Answer 1

要獲得所有的行，包括那些沒有任何比賽在status表，你需要使用一個left join代替inner join。

更改此：

INNER JOIN status ON status.id = mail_prijava.status_id 

要這樣：

LEFT JOIN status ON status.id = mail_prijava.status_id 

此外，您IFNULL線看起來很奇怪，你可能想：

IFNULL(status.opis, "test") AS status -- this will show "test" as status if it's null