具有最大和特定值的MySQL行

Question

我必須編寫一個查詢來使用所選日期和所選類別從表中檢索數據。我寫了一個查詢，並沒有按預期提供正確的數據。如果action列的值爲'AD'，它應該只查詢最大爲actiondate的行。

INSERT INTO goldstockvaluation SELECT sh.stockid, sh.description, sh.branch, sh.grossweight, sh.pureweight, sh.purity, sh.goldcarat, sh.mcpergram, sh.goldpergram, sh.fixgold, CURDATE() 
FROM stock_history sh 
JOIN (

SELECT stockid, branch,ACTION , MAX(actiondate) AS MaxDateTime 
FROM stock_history 
GROUP BY stockid,branch,ACTION 
)groupedsh ON sh.stockid = groupedsh.stockid 
AND sh.actiondate = groupedsh.MaxDateTime 
AND sh.branch = groupedsh.branch 
AND sh.action = groupedsh.action 
AND sh.branch = '8' 
AND sh.categoryid = 'G' 
AND sh.action = 'AD' 
AND sh.actiondate <= '2016-03-28 23:59:59' 

這是查詢出有action爲'AD'，並有max(actiondate)行。

Answer 1

要與max(action_date)查詢，則需要使用子查詢，例如：

select field1, field2 
from table 
where 
sh.action = 'AD' 
and sh.actiondate = (
    select max(sh.actiondate) 
     from table 
     where sh.action = 'AD' 
);