Question

你好我有这样的sql脚本。我对脚本的意图是产生今天的最高价值。但是脚本产生了意想不到的结果。任何人都可以帮我查看我的代码，看看它有什么问题吗？

脚本

SELECT   MAX(Value),
         TIMESTAMP,
         fooditem,
         cashcurren
FROM     farm1
WHERE    r.timestamp > 1405987200
         AND r.timestamp <= (1405987200 + 86400)
         AND fooditem = '2'
         AND cashcurren = '10'
GROUP BY timestamp, fooditem, cashcurren;

意外结果

Value Timestamp    fooditem   cashcurren

 200 1406029354          2         10
  84 1406034965          2         10
 536 1406034973          2         10
  70 1406035006          2         10
  63 1406035025          2         10

我想要的结果

价值时间戳fooditem cashcurren

 536 1406034973          2         10

基本上我希望我的Oracle SQL从时间戳1405987200返回到食品＃2和cashcurrency＃10的最高值到1405987200 + 86400（在这种情况下，时间戳是7/22的整天）。

Answer 1

SELECT Value, TIMESTAMP, fooditem, cashcurren
  FROM farm1 f
 WHERE timestamp between 1405987200 and (1405987200 + 86400)
   AND fooditem = '2'
   AND cashcurren = '10'
 where value =
       (select max(x.value)
          from farm1 x
         where x.timestamp between 1405987200 and (1405987200 + 86400)
           and x.fooditem = f.fooditem
           and x.cashcurren = f.cashcurren)

使用max（value）和按时间戳分组不会导致任何聚合，也没有意义。（每个时间戳可能只有一个）

上述查询使用子查询选择给定时间戳范围，fooditem和cashcurren的最大值，然后将该值提供给where子句中的查询。

Answer 2

SELECT   MAX(Value),
         TIMESTAMP,
         fooditem,
         cashcurren
FROM     farm1
WHERE    r.timestamp > 1405987200
         AND r.timestamp <= (1405987200 + 86400)
         AND fooditem = '2'
         AND cashcurren = '10'
GROUP BY timestamp, fooditem, cashcurren
order by 1 desc limit 1;

Answer 3

    SELECT   d.Value, d.TIMESTAMP, d.fooditem, d.cashcurren
    FROM     (SELECT   MAX(Value) AS 'Value',
                   TIMESTAMP,
                   fooditem,
                   cashcurren
          FROM     farm1
          WHERE    r.timestamp > 1405987200
                   AND r.timestamp <= (1405987200 + 86400)
                   AND fooditem = '2'
                   AND cashcurren = '10'
          GROUP BY timestamp, fooditem, cashcurren) AS d
    ORDER BY d.Valuse DESC limit 1;

SQL。带有最大值的时间戳问题

3 个答案: