如何在MySQL中正確使用<<colName>>？

Question

下面是我的表

| count(*) | system | 
|  2 | sys1 | 
|  7 | sys2 | 
|  6 | sys1 | 

數據我想要的輸出如下

| count(*) | system | 
|  8 | sys1 | 
|  7 | sys2 | 

我該怎麼辦呢？
以下是我正在使用的查詢。有誰能告訴我這有什麼不對嗎？

select * from 

(select count(*),system from tbl1 where creationDate < CURDATE() AND creationDate >= CURDATE() - INTERVAL 1 DAY group by system 

UNION ALL 

select count(*),system from tbl2 where creationDate < CURDATE() AND creationDate >= CURDATE() - INTERVAL 1 DAY group by system) as tbl3 group by system; 

Answer 1

你需要使用一個子查詢來實現這一目標：

試試這個：

SELECT SUM(Total) AS `Count`, system 
FROM 
(
    SELECT COUNT(*) AS Total, system FROM tbl1 
      WHERE creationDate < CURDATE() 
       AND creationDate >= CURDATE() - INTERVAL 1 DAY GROUP BY system 
    UNION ALL 
    SELECT COUNT(*) AS Total, system FROM tbl2 
      WHERE creationDate < CURDATE() 
       AND creationDate >= CURDATE() - INTERVAL 1 DAY GROUP BY system 
) A 
GROUP BY system 

OUTPUT：

| COUNT | system | 
|  8 | sys1 | 
|  7 | sys2 |