內部連接2個表的mysql查詢

Question

我想連接表A和表B並顯示每輛卡車的最新條目。

1. 表A列：TA ID，Truck_Num，SERIAL_NUM
2. 表B列：TB ID，SERIAL_NUM，緯度，經度，日期時間

希望的輸出

Truck |  DateTime  | Serial_Num |  Lat |  Long     
    1  |  datestamp |  123  |  1 |  -1          
    2  |  datestamp |  456  |  2 |  -2 

使用連接查詢

SELECT a.Truck b.Lat b.Long b.DateTime FROM TB as b INNER JOIN TA AS a a.Serial_Num=b.Serial_Num; 

我試過了，但它只是給我最近的報名時間。

SELECT a.Truck b.Lat b.Long b.DateTime FROM TB as b INNER JOIN TA AS a a.Serial_Num=b.Serial_Num WHERE b.DateTime = (SELECT MAX(b.DateTime) FROM TB tb WHERE a.Truck_Num=Truck_Num); 

Answer 1

這將顯示每輛卡車最近的項目。如果你想顯示信息的其餘部分是在所有行一樣，那麼你可以把它放在group by子句，如果沒有，那麼你必須做這個結果

SELECT Serial_Num, MAX(DateTime) FROM TB GROUP BY Serial_Num; 

這是一個連接加入你所要做的，如果數據不等於，你不能把它放在group by子句

SELECT Truck_Num, Lat, Long, maxDateTime FROM TB as b 
    INNER JOIN TA AS a ON a.Serial_Num=b.Serial_Num 
    INNER JOIN (SELECT Serial_Num, MAX(DateTime) as maxDateTime 
       FROM TB GROUP BY Serial_Num) as c 
       ON b.Serial_Num=c.Serial_Num AND maxDateTime = DateTime 

Answer 2

它應該工作，你可以檢查這個問題： Select only one row with max field with One-Many Relationship Table

SELECT 
    ta.Truck, 
    tb.Lat, 
    tb.Long, 
    MAX(tb.DateTime), 
    ta.Serial_Num as Serial_Num 
FROM 
    TB as tb 
INNER JOIN 
    TA as ta 
ON (tb.Serial_Num = ta.Serial_Num) 
GROUP BY 
    tb.Serial_Num