PHP＆MySQL問題

Question

我想知道如何檢查數組中的值，看看它是否在數據庫中，如果它不再次添加到數據庫。我將如何使用PHP & MySQL來做到這一點？

PHP代碼。

for ($x = 0; $x < count($cat_id); $x++){ 
    $cat_query = "INSERT INTO posts_categories (category_id, post_id, date_created) VALUES ('" . mysqli_real_escape_string($mysqli, strip_tags($cat_id[$x])) . "', '" . mysqli_real_escape_string($mysqli, strip_tags($post_id)) . "', NOW())"; 
} 

修改PHP代碼。

if(isset($cat_id)){ 

     for($x = 0; $x < count($cat_id); $x++){ 
      $check_query = mysqli_query($mysqli,"SELECT category_id FROM posts_categories WHERE category_id = '" . $cat_id[$x] ."' AND post_id = '" . $post_id . "'"); 

      if ($check_query == TRUE) { 
       unset($cat_id[$x]); 
      } 
     } 


     for($x = 0; $x < count($cat_id); $x++){ 
      $cat_query = "INSERT INTO posts_categories (category_id, post_id, date_created) VALUES ('" . mysqli_real_escape_string($mysqli, strip_tags($cat_id[$x])) . "', '" . mysqli_real_escape_string($mysqli, strip_tags($post_id)) . "', NOW())"; 
     } 
    } 

Answer 1

您可以使用INSERT .. ON DUPLICATE UPDATE。

Answer 2

$sql = "SELECT * FROM your_table WHERE your_column='".$yourArray['value']."'"; 
if(!mysql_num_rows(mysql_query($sql))){ 
    // no rows so add it to the database... 
} 

Answer 3

當你使用的mysqli您應該probabaly使用準備好的語句（無論從安全性和性能的角度來看）

$stmt = $mysqli->prepare("INSERT IGNORE INTO posts_categories (category_id, post_id, date_created) VALUES (?, ?, ?)"); 

// Should use a prepared statement here. 
foreach ($categories as $key => $cat) { 

    // Bind params 
    $stmt->bind_param('iis', $cat, $post_id, 'NOW()'); 

    // Exectute the query 
    $stmt->execute(); 
} 

// Close the connection! 
$mysqli->close(); 

注：我也用INSERT忽略，所以插入會失敗默默如果關鍵是存在的。