UNION並加入3個表，其中一人不具有相同的行數

Question

像這樣

$query = " 
SELECT t1.title, t1.content, t2.image, t2.tags 
FROM blog1posts t1, blog1imagestags t2 
WHERE id = :id 

UNION ALL 

SELECT t1.title, t1.content, t2.image, t2.tags 
FROM blog2posts t1, blog2imagestags t2 
WHERE id = :id 

UNION ALL //THE PROBLEM 

SELECT t1.title, t1.content, t2.tags 
FROM blog2posts t1, blog3imagestags t2 
WHERE id = :id 
"; 

我UNION或如何加入與查詢的最後一部分的查詢？

Answer 1

你可以試試這個（添加第三UNION一個空場）：

SELECT t1.title, t1.content, t2.image, t2.tags 
FROM blog1posts t1, blog1imagestags t2 
WHERE id = :id 

UNION ALL 

SELECT t1.title, t1.content, t2.image, t2.tags 
FROM blog2posts t1, blog2imagestags t2 
WHERE id = :id 

UNION ALL 

SELECT t1.title, t1.content, '' AS image, t2.tags 
FROM blog2posts t1, blog3imagestags t2 
WHERE id = :id