Question

我有一个DB表，其中包含Payment（商家，交易，TimeStamp）。对于教学交易，我们可以有多个商家。现在我想形成一个查询，其中对于（val1，val2，val3）中的事务，我们将得到做最新事务的商家.eg：

Merchant   Transaction    Time
----------------------------------
M1           T1            t1
M2           T1            t2
M1           T1             t3
M3           T2            t4
M4           T2            t5
M5           T3            t6

所以如果在（T1，T2.T3）中的transactionid，我们将得到M1（因为M1在时间t3上做了最新的T1交易），M4，M5 (t1<t2 timestamp)

Answer 1

select * from Payment
group by transaction
order by Time desc;

Answer 2

试试这个：

SELECT p.Merchant
FROM Payment p
JOIN 
(SELECT Merchant, Transaction, MAX(Time) as time 
    FROM Payment GROUP BY Merchant, Transaction) t
ON (p.Merchant = t.Merchant AND p.Transaction = t.Transaction AND p.Time = t.time)

Answer 3

SELECT Merchant FROM DB_TABLE WHERE transaction IN(T1, T2, T3) ORDER
BY Time DESC LIMIT 1

Answer 4

您可以使用Last（）函数在分割所有横切后获取最后一行。

http://www.w3schools.com/sql/sql_func_last.asp

Answer 5

您要查找的SQL语句如下：

SELECT p.Merchant, p.Transaction, p.Time
FROM Payment p
JOIN 
(SELECT Transaction, MAX(Time) as time 
    FROM Payment 
    WHERE Transaction IN('T1', 'T2', 'T3')
    GROUP BY Transaction) t
ON (p.Transaction = t.Transaction AND p.Time = t.time)

根据您的示例查看此SQLFiddle以获取结果。

关于sql查询信息

5 个答案: