如何從多個返回值中找到MAX

Question

下面是我的sql語句，一切工作正常，只是我不知道如何從多個返回值中找到MAX。無論如何，這裏是我的代碼，我有問題的部分用[]標記。

SELECT 
(product1.CNT+product2.CNT+product3.CNT)AS CNT, 
(
IFNULL(product1.SUMAMT,0)+ 
IFNULL(product2.SUMAMT,0)+ 
IFNULL(product3.SUMAMT,0) 
)AS AMTAMT, 

[MAX（product1.MXDT，product2.MXDT，product3.MXDT）AS MAXDT]

FROM 

(SELECT 
SUM(LAMT)AS SUMAMT, 
COUNT(LAMT)AS CNT, 
IFNULL(LSUBDT,(CURDATE()-INTERVAL 9999 DAY))AS MXDT 
FROM product1 WHERE LSUBBY=1 AND RECST=1 
)product1 

CROSS JOIN 
(SELECT 
SUM(LAMT)AS SUMAMT, 
COUNT(LAMT)AS CNT, 
IFNULL(LSUBDT,(CURDATE()-INTERVAL 9999 DAY))AS MXDT 
FROM product2 WHERE LSUBBY=1 AND RECST=1 
)product2 

CROSS JOIN 
(SELECT 
SUM(LAMT)AS SUMAMT, 
COUNT(LAMT)AS CNT, 
IFNULL(LSUBDT,(CURDATE()-INTERVAL 9999 DAY))AS MXDT 
FROM product3 WHERE LSUBBY=1 AND RECST=1 
)product3 

Answer 1

你正在尋找的函數被調用GREATEST：

... 
GREATEST(product1.MXDT, product2.MXDT, product3.MXDT) AS MAXDT 
....