如何使用来自另一个表的值从表中选择数据(how to select data from a table useing values from another table)

我想使用名为mergeing另一个表中的值和名为donator_1列从名为tbl_users的表中选择数据。

我尝试了以下方法：

$result = $DBcon->query("SELECT tbl_users.username, tbl_users.email, tbl_users.Phone_number FROM tbl_users,mergeing WHERE mergeing.donator_1= tbl_users.user_id AND mergeing._id = 6");
while($row = $result->fetch_array()) {
  echo '<b>' . $l['user_id'] .'</b><b>' . $l['username'] . '</b>';
}  
I want to select data from a table called tbl_users using a value from another table called mergeing and column called donator_1. 
 
I tried the following:
 
$result = $DBcon->query("SELECT tbl_users.username, tbl_users.email, tbl_users.Phone_number FROM tbl_users,mergeing WHERE mergeing.donator_1= tbl_users.user_id AND mergeing._id = 6");
while($row = $result->fetch_array()) {
  echo '<b>' . $l['user_id'] .'</b><b>' . $l['username'] . '</b>';
}  

                
最满意答案
                
                    
                        
 您可以尝试嵌套查询： 
 
SELECT username, email, Phone_number
FROM tbl_users
WHERE user_id = (SELECT donator_1 FROM mergeing WHERE _id = 6 )
 
 或内部联接： 
 
SELECT username, email, Phone_number
FROM tbl_users
JOIN mergeing ON tbl_users.user_id = mergeing.donator_1
WHERE mergeing._id = 6
You can try nested queries:
 
SELECT username, email, Phone_number
FROM tbl_users
WHERE user_id = (SELECT donator_1 FROM mergeing WHERE _id = 6 )
 
or an inner join :
 
SELECT username, email, Phone_number
FROM tbl_users
JOIN mergeing ON tbl_users.user_id = mergeing.donator_1
WHERE mergeing._id = 6