[英]Mysql query returns wrong rows
I have a simple mysql database where user has its own events table and invited events table. 我有一个简单的mysql数据库,用户具有自己的事件表和邀请事件表。
User-->>Own events (user_id is foreign key )
User and Own events-->>Invited Events(user_id is foreign key, event id is foreign key)
I want to get OWN EVENT
details from Invited Events
where user_id
is equal to some number 我想从其中
user_id
等于某个数字的Invited Events
中获得OWN EVENT
详细信息
Example: 例:
I try: 我尝试:
$user_id = $_POST["user_id"];
$stmt = $mysqli->query("SELECT A1.event_id,A1.root_folder,A1.event_name,A1.date,A1.location,A2.user_id FROM OWN_EVENTS A1, INVITED_EVENTS A2 WHERE A2.user_id=$user_id");
$rows = array();
while($r = mysqli_fetch_assoc($stmt)) {
$rows[]=$r;
}
This supposed give me (one row) event details of event_id=3
where user_id=58
but this returns all the rows in the OWN_EVENTS
table. 这应该给我(一行)
event_id=3
事件详细信息,其中user_id=58
但这将返回OWN_EVENTS
表中的所有行。
What am I doing wrong ? 我究竟做错了什么 ?
Currently, you query returns cartesian product. 当前,您查询返回的笛卡尔积。
You need to tell the optimizer how the two tables are connected with each other. 您需要告诉优化器两个表如何相互连接。
SELECT A1.event_id,A1.root_folder,A1.event_name,A1.date,A1.location,A2.user_id
FROM OWN_EVENTS A1
INNER JOIN INVITED_EVENTS A2
ON A1.columnName = A2.columnsName // columns that defines their relationship
WHERE A2.user_id=$user_id
To further gain more knowledge about joins, kindly visit the link below: 要进一步获得有关联接的知识,请访问以下链接:
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