SQL查询INNER JOIN - 意外结果

Question

我有桌子：

1. 旅行：Trip_Num，Trip_Type，Trip_Geographic等。

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

在表2中，用户进行了旅行，我需要知道旅行历史中最常见的Trip_Geographic（表1中需要知道Trip_Geographic - 他的Trip_Num旅行）。 / p>

我正在用PHP做一个项目，并且需要为特定用户（通过他的用户名）执行SQL查询 - 需要接收列为以下列的表：1。Trip_Geographic，Trip_Geographic在其中出现的计数travelers_trips_history。

附上我的表格：
的游


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的错误（检查语法），但是，我不确定查询是否会执行它应该执行的操作。

Answer 1

试试这个

    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-如果您是GroupBy Col1，则只能选择Col1或在其他列上使用聚合函数（SUM，AVG等等）

您需要查看Rules for GroupBy并更好地了解它。

在评论后修改：

$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

试试这个

问题是你的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GROUP By之后的Haing WHERE子句并使用不在GROUPED BY或AGGREGATE函数中的列。 尝试以下具有用户名，trip_geographic和旅行次数的。

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