多個WHERE在MySQL語句中給我帶來麻煩

Question

我使用CodeIgniter的db類來創建查詢。

查詢最終看起來像這樣;

SELECT `user_id`, `firstname`, `lastname`, `email`, `school_id`, `country_id` 
    FROM (`users`) 
    WHERE `user_id` != '1' 
    AND `firstname` = 'thomas' 
    OR `lastname` = 'thomas' 
    OR `email` = 'thomas' 
    OR `firstname` = 'jefferson' 
    OR `lastname` = 'jefferson' 
    OR `email` = 'jefferson' 

在這種情況下，用戶搜索「托馬斯·傑斐遜」和用戶自己的ID爲1。因此，要確保用戶無法搜索自己會檢查，以便user_id是不是1。

我知道查詢並不好，但它完全適用於什麼，我需要它，以及我是懶得做是正確的。

這一切背後的PHP代碼是

$this->db->select('user_id, firstname, lastname, email, school_id, country_id')->from('users'); 
    $this->db->where('user_id !=', $this->session->userdata('user_id')); 
    for ($i = 0; $i < count($searchQuery); $i++) { 
     if ($i == 0) { 
      $this->db->where('firstname', $searchQuery[$i])->or_where('lastname', $searchQuery[$i])->or_where('email', $searchQuery[$i]); 
     } else { 
      $this->db->or_where('firstname', $searchQuery[$i])->or_where('lastname', $searchQuery[$i])->or_where('email', $searchQuery[$i]); 
     } 
    } 
    $this->db->limit(10); 
    $query = $this->db->get(); 

我99％肯定的是，

WHERE `user_id` != '1' 
    AND(<-- this) `firstname` = ... 

是錯誤的，但我似乎無法找出一種不同的方式做它。

Answer 1

以SQL Server中的看Operation Precedence。
在那裏你會發現，AND操作之前OR操作評估。

這意味着您的查詢首先評估AND：

user_id != '1' AND firstname = 'thomas'

然後

OR blablablablabla (the rest of the query)

爲了使它糾正它會只是這樣的：

SELECT `user_id`, `firstname`, `lastname`, `email`, `school_id`, `country_id` 
    FROM (`users`) 
    WHERE `user_id` != '1' 
    AND (`firstname` = 'thomas' 
    OR `lastname` = 'thomas' 
    OR `email` = 'thomas' 
    OR `firstname` = 'jefferson' 
    OR `lastname` = 'jefferson' 
    OR `email` = 'jefferson') 

Answer 2

嘗試這樣

SELECT `user_id`, `firstname`, `lastname`, `email`, `school_id`, `country_id` 
FROM (`users`) 
WHERE `user_id` != 1 
AND 
(`firstname` = 'thomas' 
OR `lastname` = 'thomas' 
OR `email` = 'thomas' 
OR `firstname` = 'jefferson' 
OR `lastname` = 'jefferson' 
OR `email` = 'jefferson') 

Answer 3

你要組織括號，在這種形式... 選擇user_id，firstname，lastname，email，school_id，country_id FROM（users） WHERE user_id！= '1' AND（firstname = '托馬斯' OR lastname = '托馬斯' OR email = '托馬斯' OR firstname ='傑弗遜''jefferson' 或email ='jefferson'）

Answer 4

感謝您的回答！我通過這樣做來固定它;

$sql = "SELECT user_id, firstname, lastname, email, school_id, country_id FROM users WHERE user_id != " . $this->session->userdata('user_id'); 
    $firstname = array(); 
    $lastname = array(); 
    $email = array(); 

    foreach ($searchQuery as $a) 
    { 
     if (! empty($a)) 
     { 
      $firstname[] = "'".$a."'"; 
      $lastname[] = "'".$a."'"; 
      $email[] = "'".$a."'"; 
     } 
    } 
    $firstname = implode(',', $firstname); 
    $lastname = implode(',', $lastname); 
    $email = implode(',', $email); 

    $sql .= " AND(firstname IN($firstname) OR lastname IN($lastname) OR email IN($email))"; 

    $query = $this->db->query($sql); 

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