如果mysql数据库中存在数据，则使用它，否则使用占位符数据 - If data exists in mysql database use it else use placeholder data

If data exists in mysql database use it else use placeholder data

我想做的是显示一些数据从mysql数据库，如果它由用户设置，如果它没有设置，那么我只是想显示一些占位符或"dummy"数据。例如，如果用户创建个人资料，他将默认情况下得到一些随机或占位符图片作为个人资料图片，当他改变它，我想显示从数据库的图片。同样的道理也适用于用户描述或"关于我"部分。

这是我目前得到的

<?php 
$getInfo = $con->prepare("SELECT * FROM user_info WHERE userid=:userid");
$getInfo->execute(array(':userid'=>$userID));
$data = $getInfo->fetch(PDO::FETCH_ASSOC);
$description = $data['description'];
?>
<div class="container">
  <div class="row">
    <div class="col-sm-12">
      <h3 class="page-title">USER DESCRIPTION</h3>
      <?php if(!empty($description)) {
        echo '<p>' . $description . '</p>';
      } else { ?>
      <p>Lorem ipsum dolor sit amet, consectetur adipisicing elit. Tenetur incidunt, at error. Provident veritatis ratione laborum modi laudantium, quidem inventore facilis at qui blanditiis, sunt tempore labore sit, eligendi libero?</p>
      <?php } ?>
    </div>
  </div>
</div>

所以在这里我使用!empty($description)，但我不确定这是否是正确的方法来做到这一点，如果这总是要工作。我是mysql和php的新手，这只是为了学习目的。添加$userID是用户登录时存在的会话

假设始终定义了$data['description']，则可以正常工作。但是，最好将逻辑和表示分开。

<?php 
$getInfo = $con->prepare("SELECT * FROM user_info WHERE userid=:userid");
$getInfo->execute(array(':userid'=>$userID));
$data = $getInfo->fetch(PDO::FETCH_ASSOC);
$description = !empty($data['description']) ? $data['description'] : 'Lorem ipsum dolor sit amet, consectetur adipisicing elit. Tenetur incidunt, at error. Provident veritatis ratione laborum modi laudantium, quidem inventore facilis at qui blanditiis, sunt tempore labore sit, eligendi libero?';
?>
<div class="container">
  <div class="row">
    <div class="col-sm-12">
      <h3 class="page-title">USER DESCRIPTION</h3>
        <p>
          <?php echo $description; ?>
        </p>
    </div>
  </div>
</div>

你也可以直接在MySQL

你总是得到一个结果。如果没有找到userid，则从UNION

返回2 SELECT。

SELECT * FROM (
  SELECT * FROM j WHERE userid =99999
  UNION ALL
  SELECT 0,'NOOOOOOOOO'
  ) AS c ORDER BY userid DESC LIMIT 1;

where the Table

MariaDB [tmp]> select * from j;
+--------+-------+
| userid | bame  |
+--------+-------+
|      0 | 222   |
|      1 | a     |
|     22 | b     |
|     47 | c     |
|    333 | d     |
|    334 | fff   |
|    335 | hhh   |
|   NULL | hallo |
+--------+-------+
8 rows in set (0.00 sec)

和2个样本

MariaDB [tmp]> SELECT * FROM (   SELECT * FROM j WHERE userid =1   UNION ALL   SELECT 0,'NOOOOOOOOO'   ) AS c ORDER BY userid DESC LIMIT 1;
+--------+------+
| userid | bame |
+--------+------+
|      1 | a    |
+--------+------+
1 row in set (0.00 sec)
MariaDB [tmp]> SELECT * FROM (   SELECT * FROM j WHERE userid =99999   UNION ALL   SELECT 0,'NOOOOOOOOO'   ) AS c ORDER BY userid DESC LIMIT 1;
+--------+------------+
| userid | bame       |
+--------+------------+
|      0 | NOOOOOOOOO |
+--------+------------+
1 row in set (0.00 sec)
MariaDB [tmp]>