Php 合并多个SQL查询的结果（由于列名不同，因此无法合并）

我想做一个通知页面，显示关于各种事情的通知，比如新关注者、新喜欢、新评论等。我想显示一个列表，按时间顺序显示所有这些事情

我的桌子是这样的：

COMMENT
1   comment__id
2   comment__user_id
3   comment__snap__id
4   comment__text
5   comment_add_time

LIKE
1   like__id
2   like__user__id
3   like__snap__id
4   like__like_time

FOLLOW
1   follow__id
2   follower__user__id
3   followed__user__id
4   follow__follow_time
5   follow__request_status

try {
    $select_followers_query = '
    SELECT follow.follower__user__id, follow.followed__user__id, follow.follow__request_status, user.user__id, user.user__username, user.user__profile_picture, user.privacy
    FROM follow
    JOIN user ON(follow.follower__user__id = user.user__id) 
    WHERE followed__user__id = :followed__user__id';
    $prep_select_followers = $conn->prepare($select_followers_query);
    $prep_select_followers->bindParam(':followed__user__id', $get_user__id, PDO::PARAM_INT);
    $prep_select_followers->execute();
    $followers_result = $prep_select_followers->fetchAll();
    $followers_count = count($followers_result);
}   
catch(PDOException $e) {
    $conn = null;
    echo $error;
}

foreach($followers_result AS $followers_row) {
    $follower_user_id = $followers_row['follower__user__id'];
    // the rest of the variables will come here...
}

@user_1 liked your photo
@user_4 started following you
@user_2 commented on your photo
etc...

我会用如下查询加载用户的追随者：

COMMENT
1   comment__id
2   comment__user_id
3   comment__snap__id
4   comment__text
5   comment_add_time

LIKE
1   like__id
2   like__user__id
3   like__snap__id
4   like__like_time

FOLLOW
1   follow__id
2   follower__user__id
3   followed__user__id
4   follow__follow_time
5   follow__request_status

try {
    $select_followers_query = '
    SELECT follow.follower__user__id, follow.followed__user__id, follow.follow__request_status, user.user__id, user.user__username, user.user__profile_picture, user.privacy
    FROM follow
    JOIN user ON(follow.follower__user__id = user.user__id) 
    WHERE followed__user__id = :followed__user__id';
    $prep_select_followers = $conn->prepare($select_followers_query);
    $prep_select_followers->bindParam(':followed__user__id', $get_user__id, PDO::PARAM_INT);
    $prep_select_followers->execute();
    $followers_result = $prep_select_followers->fetchAll();
    $followers_count = count($followers_result);
}   
catch(PDOException $e) {
    $conn = null;
    echo $error;
}

foreach($followers_result AS $followers_row) {
    $follower_user_id = $followers_row['follower__user__id'];
    // the rest of the variables will come here...
}

@user_1 liked your photo
@user_4 started following you
@user_2 commented on your photo
etc...

接下来，我得到如下结果：

COMMENT
1   comment__id
2   comment__user_id
3   comment__snap__id
4   comment__text
5   comment_add_time

LIKE
1   like__id
2   like__user__id
3   like__snap__id
4   like__like_time

FOLLOW
1   follow__id
2   follower__user__id
3   followed__user__id
4   follow__follow_time
5   follow__request_status

try {
    $select_followers_query = '
    SELECT follow.follower__user__id, follow.followed__user__id, follow.follow__request_status, user.user__id, user.user__username, user.user__profile_picture, user.privacy
    FROM follow
    JOIN user ON(follow.follower__user__id = user.user__id) 
    WHERE followed__user__id = :followed__user__id';
    $prep_select_followers = $conn->prepare($select_followers_query);
    $prep_select_followers->bindParam(':followed__user__id', $get_user__id, PDO::PARAM_INT);
    $prep_select_followers->execute();
    $followers_result = $prep_select_followers->fetchAll();
    $followers_count = count($followers_result);
}   
catch(PDOException $e) {
    $conn = null;
    echo $error;
}

foreach($followers_result AS $followers_row) {
    $follower_user_id = $followers_row['follower__user__id'];
    // the rest of the variables will come here...
}

@user_1 liked your photo
@user_4 started following you
@user_2 commented on your photo
etc...

我将有单独的SQL查询，就像上面的查询一样，每个查询都会加载一些内容。上面的示例加载追随者，另一个查询将加载评论等。我想显示所有这些查询的结果，并按时间顺序显示它们，如下所示：

COMMENT
1   comment__id
2   comment__user_id
3   comment__snap__id
4   comment__text
5   comment_add_time

LIKE
1   like__id
2   like__user__id
3   like__snap__id
4   like__like_time

FOLLOW
1   follow__id
2   follower__user__id
3   followed__user__id
4   follow__follow_time
5   follow__request_status

try {
    $select_followers_query = '
    SELECT follow.follower__user__id, follow.followed__user__id, follow.follow__request_status, user.user__id, user.user__username, user.user__profile_picture, user.privacy
    FROM follow
    JOIN user ON(follow.follower__user__id = user.user__id) 
    WHERE followed__user__id = :followed__user__id';
    $prep_select_followers = $conn->prepare($select_followers_query);
    $prep_select_followers->bindParam(':followed__user__id', $get_user__id, PDO::PARAM_INT);
    $prep_select_followers->execute();
    $followers_result = $prep_select_followers->fetchAll();
    $followers_count = count($followers_result);
}   
catch(PDOException $e) {
    $conn = null;
    echo $error;
}

foreach($followers_result AS $followers_row) {
    $follower_user_id = $followers_row['follower__user__id'];
    // the rest of the variables will come here...
}

@user_1 liked your photo
@user_4 started following you
@user_2 commented on your photo
etc...

---

我怎样才能做到这一点？SQL UNION要求表具有相同的列数，并且所选列必须具有相同的名称。我没有这些。此外，每种结果（关注者、评论等）都会有不同的标记。关注者通知将有一个follow按钮，注释通知将有一个重定向到喜欢的照片的按钮等。

您可以使用UNION，但需要使用“AS”为列指定相同的名称。 您还需要在每个选择中添加一行，如下所示：

, 'comment' as Type FROM comment

以及：

, 'follow' as Type FROM follow

SQL UNION要求表具有相同的列数，并且所选列必须具有相同的名称

不，没有。表“a”有两列，integer和varchar

create table a (
  a_id integer,
  a_desc varchar(10)
);
insert into a values (1, 'aaaaaaaa'), (2, 'bbbbbbbb');

表“b”有三列，varchar、date和char

create table b (
  b_id varchar(10),
  created_date date,
  unused char(1)
);

insert into b values ('xyz', '2014-01-01', 'x'), ('tuv', '2014-01-13', 'x');

SQL union运算符只要求SELECT子句（而不是表）具有相同的列数，并且它们具有兼容的数据类型。您通常可以将不兼容的类型转换为更有用的类型

-- SELECT clause has three columns, but table "a" has only two.
-- The cast is for illustration; MySQL can union an integer with a 
-- varchar without a cast.
--
select cast(a_id as char) as col_1, a_desc as col_2, null as col_3
from a
union all
-- Note that these columns don't have the same names as the columns
-- above.
select b_id, null, created_date 
from b;

可以使用单个列来表示date和varchar，但这通常不是一个好主意。（把日期和显然不是日期的东西混在一起通常不是个好主意。）

---

“SQL UNION要求表具有相同的列数，并且所选列必须具有相同的名称。”您错了。有几种方法可以解决工会的表格和列要求。“你错了。有几种方法可以解决工会的表格和列要求”-启发我。我找不到这方面的任何信息………您需要使用“AS”为列指定相同的名称“不，您没有。谢谢您的详细解释！