使用外鍵從其他表中獲取數據

Question

每個cursus有一個cursussoort連接外鍵我有2個表。 我試圖從cursussoort表中獲取數據以顯示在while循環中。 cursussoort_ID顯示的ID是顯而易見的，但是如何從cursussoort表中獲取'naam'？

<?php
$result = mysqli_query($con, "SELECT * FROM cursus WHERE cursussoort_ID = 1 ORDER BY begindatum ASC");
while ($cursus = mysqli_fetch_array($result)) {
?>
<div class="col-lg-8 col-lg-offset-2 col-md-10 col-md-offset-1">
  <div class="post-preview">
      <h2 class="post-title">
        <?php echo $cursus['cursussoort_ID'];?>
        <?php echo $cursus['begindatum'] . "<br />";?>

      </h2>
      <h3 class="post-subtitle">
        <?php echo $cursus['beschrijving'] . "<br />";?>
      </h3>
  </div>
</div>
<?php } ?>

Answer 1

你應該JOIN在SQL語句從2個表連接數據：

SELECT c.*, cs.* FROM cursus c 
INNER JOIN cs.cursussoort ON c.cursussoort_ID = cs.ID 
WHERE c.cursussoort_ID = 1 
ORDER BY begindatum ASC

然后你可以用HTML顯示它：

<?php
$result = mysqli_query($con, "SELECT c.*, cs.* FROM cursus c INNER JOIN cs.cursussoort ON c.cursussoort_ID = cs.ID WHERE c.cursussoort_ID = 1 ORDER BY begindatum ASC");
while ($cursus = mysqli_fetch_array($result)) {
?>
<div class="col-lg-8 col-lg-offset-2 col-md-10 col-md-offset-1">
  <div class="post-preview">
      <h2 class="post-title">
        <?php echo $cursus['cursussoort_ID']; ?>
        <?php echo $cursus['naam']; ?><br />
        <?php echo $cursus['begindatum']; ?><br />
      </h2>
      <h3 class="post-subtitle">
        <?php echo $cursus['beschrijving']; ?><br />
      </h3>
  </div>
</div>
<?php } ?>

Answer 2

在表之間執行JOIN

SELECT c.* 
FROM cursus c
JOIN  cursussoort cr ON c.ID = cr.cursussoort_ID
WHERE c.cursussoort_ID = 1 
ORDER BY c.begindatum

Answer 3

嘗試左外連接

主查詢是

`SELECT * FROM cursus c LEFT OUTER JOIN cursussoort cr ON (c.cursussoort_ID = cr.id)  WHERE cursussoort_ID = 1 ORDER BY c.begindatum ASC`