生成過去幾個月並加入無關數據

Question

在MySQL或MSSQL中，我需要生成一個結果集，該結果集將返回最近三個月按月份分組的qheader。所以我有questionsec表模式

+-----------+ 
|questionsec| 
+-----------+ 
|qid (PK) | 
|qheader | 
+-----------+ 

後

(select * from questionsec) 

我得到：

+-------+------+ 
|qid| qheader | 
+---|----------+ 
| 1 | QH1  | 
| 2 | QH2  | 
+---+----------+ 

什麼是我需要編寫生成以下結果集查詢：

+-------+---------+ 
|month | qheader | 
+-------|---------+ 
|2014-09| QH1  | 
|2014-09| QH2  | 
|2014-10| QH1  | 
|2014-10| QH2  | 
|2014-11| QH1  | 
|2014-11| QH2  | 
+-------+---------+ 

我知道以下情形將產生（在MySQL）過去三個月，但不知道如何加入到每個月份行每qheader在questionsec

SELECT DATE_FORMAT(now()- INTERVAL 1 MONTH,'%Y-%m') as month 
UNION ALL SELECT DATE_FORMAT(now()- INTERVAL 2 MONTH,'%Y-%m') 
UNION ALL SELECT DATE_FORMAT(now()- INTERVAL 3 MONTH,'%Y-%m') 

Answer 1

CREATE TABLE questionsec(qid INT NOT NULL,qheader CHAR(3)); 

INSERT INTO questionsec VALUES (1,'QH1'),(2,'QH2'); 

SELECT qheader,month FROM questionsec x JOIN (SELECT '2014-09' month UNION SELECT '2014-10' UNION SELECT '2014-11')y; 
+---------+---------+ 
| qheader | month | 
+---------+---------+ 
| QH1  | 2014-09 | 
| QH2  | 2014-09 | 
| QH1  | 2014-10 | 
| QH2  | 2014-10 | 
| QH1  | 2014-11 | 
| QH2  | 2014-11 | 
+---------+---------+