从两个mysql表中获取数据，其中一个表的行与另一个表的行连接

Question

I have two mysql database table, one is for posts and other is for comments.

Post table

+----+-------+
| ID | texts |
+----+-------+
| 1  | abc   |
| 2  | xyz   |
+----+-------+

And comments table

+----+--------+-------+
| ID | postid | texts |
+----+--------+-------+
| 1  | 1      | abc1  |
| 2  | 1      | abc2  |
| 3  | 1      | abc3  |
| 4  | 2      | xyz1  |
| 5  | 2      | xyz2  |
+----+--------+-------+

Now, How to get posts with bare minimum mysql query requests, so that output is like,

$data = array(
    0 => array(
        ID => 1,
        texts => abc,
        comments => array(
            0 => array(
                ID => 1,
                texts => abc1
            )
            1 => array(
                ID => 2,
                texts => abc2
            )
            2 => array(
                ID => 3,
                texts => abc3
            )
        )
    )
    1 => array(
        ID => 2,
        texts => xyz,
        comments => array(
            0 => array(
                ID => 4,
                texts => xyz1
            )
            1 => array(
                ID => 5,
                texts => xyz2
            )
        )
    )
)

Answer 1

How about

SELECT  *
FROM    Post p LEFT JOIN
        Comments c  ON  p.ID = c.postID

Answer 2

It will be helpful if you can provide code to put results in array

Let me first recommend a better multidimensional array that will be easier to work with.

Array Format:

$data = array(
    post.ID => array(
        "texts" => post.texts,
        "comments" => array(
            comments.ID => comments.texts,
        ),
    ),
);

The above format will be easier to work with especially for direct access into the array and also for the foreach loop.

Now for assigning the data from the MySQL result into the array using mysqli_* functions and a while loop do the following:

//connect to mysql database
$link = $mysqli_connect("localhost","your_user","your_password","your_database");
//form mysql query
$query = "
    SELECT
        post.ID AS post_id,
        post.texts AS post_texts,
        comments.ID AS comments_id,
        comments.texts AS comments_texts
    FROM
        post
        LEFT JOIN comments ON (comments.postid = post.ID)
    WHERE
        posts.ID < 10
";
//run mysql query and return results
$mysqli_result = mysqli_query($link,$query);
//define empty $data array
$data = array();
//loop through result sets fetching string array with each result row
while($row = mysqli_fetch_array($mysqli_result)){
    //set the post text if not already set
    if(!isset($data[$row["post_id"]]["texts"])){
        $data[$row["post_id"]]["texts"] = $row["post_texts"];
    }
    //set the comments data if not NULL otherwise set comments to empty array to maintain structure
    if(!empty($row["comments_id"])){
        $data[$row["post_id"]]["comments"][$row["comments_id"]] = $row["comments_texts"];
    } else {
        $data[$row["post_id"]]["comments"] = array();
    }
}
//free the results set
mysqli_free_result($mysqli_result);
//close connection to mysql database
mysqli_close($link);

//print out the post text with the id of 1 with two line breaks
//be careful using this method unless you are sure that post with id of 1 exists or first check if(isset($data["1"])){...}
print $data["1"]["texts"]."<br /><br />";

//loop through all of the comments for a particular post with id of 1
foreach($data["1"]["comments"] as $key => $value){
    //print out the comment id with a line break
    print "Comment ID: ".$key."<br />";
    //print out the comments texts with two line breaks
    print "Comment: ".$value."<br /><br />";
}

//loop through and print all the post texts and how many comments exist for the post
foreach($data as $key => $value){
    //print the post ID with a line break
    print "Post ID: ".$key."<br />";
    //print the post texts with a line break
    print "Post: ".$value["texts"]."<br />";
    //count the number of comments
    $num_comments = count($value["comments"]);
    //get correct plural form of noun
    ($num_comments==1) ? $comments = "comment" : $comments = "comments";
    //print the number of comments for the post with two line breaks
    print $num_comments." ".$comments." for this post.<br /><br />";
}