Question

我有一个查询应该从每个price_per_pax_after_tax backend_hotels_id和date_start中选择最低的package_supplier，这似乎一直有效，直到我添加一个WHERE子句。

以下是查询：

SELECT e.price_per_pax_after_tax, e.hotel_score, e.package_id, e.package_type
FROM packages_sorted_YQU e
INNER JOIN (
  SELECT db_id, MIN( price_per_pax_after_tax ) AS lowest_price, package_id, hotel_score
  FROM `packages_sorted_YQU`
  WHERE `package_type` IN ('9', '10', '18') 
  AND `package_duration` IN ('6', '8', '12')
  GROUP BY 
    `date_start` , `package_supplier` , `backend_hotels_id`
) AS j 
ON j.db_id = e.db_id
AND j.lowest_price= e.price_per_pax_after_tax
AND j.hotel_score = e.hotel_score
AND j.package_id = e.package_id;

表格很大但列出的所有字段都是INT，除了date_start是DATE

导致问题的where子句是：

WHERE `package_type` IN ('9', '10', '18') 
AND `package_duration` IN ('6', '8', '12')

如果没有where子句，我会获得超过400个结果，并且使用where子句我得到零结果:(非常感谢任何帮助。

Answer 1

如果您的列package_type和package_duration的类型为int，则不必像'那样将值包装在字符串中。

SELECT e.price_per_pax_after_tax, e.hotel_score, e.package_id, e.package_type
FROM packages_sorted_YQU e
INNER JOIN (
  SELECT db_id, MIN( price_per_pax_after_tax ) AS lowest_price, package_id, hotel_score
  FROM `packages_sorted_YQU`
  WHERE `package_type` IN (9, 10, 18) 
  AND `package_duration` IN (6, 8, 12)
  GROUP BY 
    `date_start` , `package_supplier` , `backend_hotels_id`
) AS j 
ON j.db_id = e.db_id
AND j.lowest_price= e.price_per_pax_after_tax
AND j.hotel_score = e.hotel_score
AND j.package_id = e.package_id;

Answer 2

子查询：

  SELECT db_id
       , MIN( price_per_pax_after_tax ) AS lowest_price
       , package_id
       , hotel_score
  FROM `packages_sorted_YQU`
  WHERE `package_type` IN ('9', '10', '18') 
  AND `package_duration` IN ('6', '8', '12')
  GROUP BY 
       `date_start` 
     , `package_supplier` 
     , `backend_hotels_id`

无论是否有WHERE子句，

都会产生不确定的结果。因为您按date_start, package_supplier, backend_hotels_id进行分组，并且在SELECT列表列中没有任何汇总函数：db_id, package_id, hotel_score。

如果(date_start, package_supplier, backend_hotels_id)是主键或唯一，则此查询应始终如一。

哪个是表格的PRIMARY KEY，还有其他UNIQUE个密钥吗？

Answer 3

大家好，感谢您的宝贵意见。我已经在没有子查询的情况下解决了问题，而且它的工作速度也快了。

SELECT MIN
(
    concat
    (
        LPAD(`price_per_pax_after_tax` , 5, '0'),
        LPAD(`package_id` , 12, '0'),
        LPAD(`hotel_score` , 7, '0')
    )
) AS cat
FROM `packages_sorted_YQU`
WHERE `package_type` IN
(
    9, 10, 18
)
AND `package_duration` IN
(
    6, 7, 8
)
GROUP BY `date_start` , `package_supplier` , `backend_hotels_id`

然后在PHP中我将串联分解为：

while($r=mysql_fetch_array($q,MYSQL_ASSOC))
{
    $a[lrp][] = intval(substr($r[cat], 0, 5));
    $a[package_id][] = intval(substr($r[cat], 5, 12));
    $a[hotel_score][] = substr($r[cat], 17, 7);
}

我很幸运，唯一的FLOAT值是hotel_score所以我把它放在最后 - 其他两个是INT类型

苦苦挣扎将WHERE子句添加到INNER JOIN

3 个答案: