（Php）检索上一个表的主键并插入当前表

Question

我是php脚本的新手..我想知道我的php脚本中是否有任何错误，我想从收入表中获取income_id（收入表中的主键）并将其插入费用表（作为外键） ...我可以将所有数据添加到费用表中，除了income_id ..

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<?php 

 //Importing our db connection script
 require_once('dbConnect.php');

 if($_SERVER['REQUEST_METHOD']=='POST'){
 
 //Getting values
 $id = $_POST['id'];
 $income_id = $_POST['income_id'];
 $category = $_POST['category'];
 $amount = $_POST['amount'];
 $date = date('Y-m-d');

 $sql = "SELECT income_id from `income` where id='".$id."'";
 $result = mysqli_query($con, $sql);
 $rows = mysqli_fetch_array($result);

 //Creating an sql query
 $sql = "INSERT INTO expenses (income_id,category,amount,date) VALUES ('$rows[income_id]','$category','$amount','$date')";
 
 //Executing query to database
 if(mysqli_query($con,$sql)){
 echo 'Added Successfully';
 }else{
 echo 'Could Not Add';
 }
 
 //Closing the database 
 mysqli_close($con);
 }

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Answer 1

我建议加入两个查询：

INSERT INTO expenses (income_id, category, amount, date)
VALUES ((SELECT income_id FROM `income` WHERE id='$id'), '$category', '$amount', '$date')