如何在多对多关系中只重复一次行

Question

我正在 php 上处理多对多关系我有 3 tables ，电影 table 其中包含电影名称和电影 ID 流派 table 包含流派和流派 ID 和 movie_genre table 具有电影 ID 和流派 ID
流派 table 具有这些值

(1 ,'action'),
(2 ,'comedy'),
(3 ,'drama'),
(4 ,'mystery');

我使用下面的代码来获取数据

 $query = " SELECT movie_name,movie_id,genre FROM movies
    JOIN movie_genre ON movies.movie_id = movie_genre.movie_id
    JOIN genre ON movie_genre.genre_id = genre.genre_id
    WHERE movie.movie_id = ?";


    $stmt = mysqli_prepare($conn, $query);
    $stmt->bind_param('i', $id);
    $stmt->execute();
    $result = $stmt->get_result();
    if(mysqli_num_rows($result) > 0 ){
    while ($row = mysqli_fetch_assoc($result)) {

    echo ' movie_id: '.$row["movie_id"].' movie name:'.$row["movie_name"].'
    Genres:' .$row["genre"]

        }}

但结果会像
movie_id movie_name 流派[1]
movie_id movie_name 流派[2]
movie_id movie_name 流派[3]
一个例子

movie_id:55 movie name: titanic genre : action 

movie_id:55 movie name: titanic genre : drama

movie_id:55 movie name: titanic genre : romance

我想要的结果是

movie_id:55 movie name: titanic genre : action drama romance

我确实尝试使用限制 1，但结果只显示第一种类型

Answer 1

您可以使用 GROUP_CONCAT 和 GROUP BY:

SELECT movie_name,movie_id, GROUP_CONCAT(genre SEPARATOR ' ') AS genre
FROM movies
JOIN movie_genre ON movies.movie_id = movie_genre.movie_id
JOIN genre ON movie_genre.genre_id = genre.genre_id
WHERE movie.movie_id = ?
GROUP BY movie_name,movie_id

Answer 2

只需要为流派做一个循环我无法测试这个，所以这只是把我想象的会起作用的东西放在一起，但它会一直存在这些行，这里可能有语法错误

$query = " SELECT movie_name,movie_id,genre FROM movies
    JOIN movie_genre ON movies.movie_id = movie_genre.movie_id
    JOIN genre ON movie_genre.genre_id = genre.genre_id
    WHERE movie.movie_id = ?";    

    $stmt = mysqli_prepare($conn, $query);
    $stmt->bind_param('i', $id);
    $stmt->execute();
    $result = $stmt->get_result();
    if(mysqli_num_rows($result) > 0 ){

    // if it's greater than zero, great, we have at least 1 movie.
    // but if it's greater than 1, then we know we have more than 1 genre

    while ($row = mysqli_fetch_assoc($result)) {
    echo 'movie_id:'.$row["movie_id"].'movie name:'.$row["movie_name"];
    break; // so it only runs through this loop once, instead of using limit
    }//end while

    if(mysqli_num_rows($result) > 1 ){
    // more than 1 genre so loop and print out just genres
    while ($row = mysqli_fetch_assoc($result)) {    
      echo $row["genre"];    
    }//end while
    }//end if more than 1 genre
    }//end if

如何在多对多关系中只重复一次行

how to repeat rows only once in many to many relationship

php

mysql

sql

mysqli

join