SQL查询INNER JOIN-意外结果

Question

我有桌子：

1. 行程：Trip_Num，Trip_Type，Trip_Geographic等。

2. Travellers_trips_history：用户名，Trip_Num，Trip_Type，Trip_Season等。

在表2中，有用户进行的旅行，我需要知道他的旅行历史上最常见的Trip_Geographic（表1需要了解Trip_Geographic-他的Trip_Num进行的旅行）。

我正在用PHP执行一个项目，并且需要针对特定​​用户（通过其用户名）执行SQL查询-需要接收一个表，这些表的列为：1. Trip_Geographic，Trip_Geographic在travellers_trips_history中出现的次数。

附上我有的表：
旅行

travelers_trips_history

我做的查询：

$query = "select traveler_trips_history.*, COUNT(trips.Trip_Geographic) AS Trip_Geographic_occurrence 
FROM traveler_trips_history INNER JOIN trips ON 
travelers_trips_history.Trip_Num = trips.Trip_Num 
GROUP BY Trip_Geographic 
ORDER BY Trip_Geographic_occurrence DESC
WHERE traveler_trips_history.Traveler_Username = $username";

我收到有关Group BY（检查语法）的错误，但是，我不确定查询将执行应做的事情。

Answer 1

尝试这个

    SELECT traveler_trips_history.*
    ,COUNT(trips.Trip_Geographic) AS Trip_Geographic_occurrence
FROM traveler_trips_history
INNER JOIN trips ON travelers_trips_history.Trip_Num = trips.Trip_Num
WHERE traveler_trips_history.Traveler_Username = $USERNAME
GROUP BY traveler_trips_history.travelers_trips_history
    ,traveler_trips_history.Username
    ,traveler_trips_history.Trip_Num
    ,traveler_trips_history.Trip_Type
    ,traveler_trips_history.Trip_Season
ORDER BY Trip_Geographic_occurrence DESC

Answer 2

您的查询中有2个问题：

1-您应该在GroupBy子句之前有where子句

2-如果对Col1进行分组，则只能选择Col1或在其他列（SUM，AVG等）上使用聚合函数

您需要检查GroupBy规则并更好地理解它。

评论后编辑：

$query = "select Trip_Geographic, COUNT(*) AS Trip_Geographic_occurrence 
FROM traveler_trips_history INNER JOIN trips ON 
travelers_trips_history.Trip_Num = trips.Trip_Num 
WHERE traveler_trips_history.Traveler_Username = $username
GROUP BY Trip_Geographic 
ORDER BY Trip_Geographic_occurrence DESC";

Answer 3

这样尝试

问题是您的where子句和按列分组。

     SELECT tr.Trip_Geographic
    ,COUNT(hs.*) AS Trip_Geographic_occurrence
FROM traveler_trips_history hs
INNER JOIN trips tr ON hs.Trip_Num = tr.Trip_Num
WHERE hs.Username = $USERNAME
GROUP BY tr.Trip_Geographic
ORDER BY Trip_Geographic_occurrence DESC

Answer 4

您的问题是在GROUP BY之后使用WHERE子句，并使用不在GROUPED BY或AGGREGATE函数中的列。 尝试使用以下用户名，trip_geographic和旅行次数。

select traveler_trips_history.Traveler_Username, traveler_trips_history.Trip_Geographic, COUNT(trips.Trip_Geographic) AS Trip_Geographic_occurrence 
FROM traveler_trips_history INNER JOIN trips ON 
travelers_trips_history.Trip_Num = trips.Trip_Num 
GROUP BY Trip_Geographic, traveler_trips_history.Traveler_Username
having traveler_trips_history.Traveler_Username = $username
ORDER BY Trip_Geographic_occurrence DESC