MySQL更新或插入沒有主鍵的表格

Question

我知道執行更新或插入的簡單方法是使用'REPLACE'，但它需要一個主鍵，在沒有主鍵的情況下如何？

我在表5列：

1. remark_id（自動遞增的主鍵）
2. USER_ID
3. remark_user_id
4. 此言
5. LAST_MODIFIED

我希望檢查一下user_id和remark_user_id在更新備註之前先存在，否則將創建一個新行以將備註保存爲user_id和remark_user_id。

這裏是我的代碼

INSERT INTO `users_remark` (`user_id`, `remark_user_id`, `remark`) 
SELECT 1,3 ,'testing123' 
FROM dual 
WHERE NOT EXISTS 
    (SELECT * 
    FROM `users_remark` 
    WHERE `user_id` = 1 
     AND `remark_user_id` = 3) 

運行SQL後，什麼也沒有發生在我的數據庫。沒有添加或更新記錄。

[編輯]

代碼更改使用IF...ELSE...但它與一些語法錯誤的第一行

#1064 - You have an error in your SQL syntax; check the manual that corresponds to your MySQL server version for the right syntax to use near 'IF EXISTS (SELECT * FROM users_remark WHERE user_id' at line 1 

IF EXISTS (
    SELECT * FROM `users_remark` 
    WHERE `user_id`=1 AND `remark_user_id` = 3 
    ) 
    THEN UPDATE `users_remark` SET `remark` = 'testing123' 
      WHERE `user_id`=1 AND `remark_user_id` = 3 
ELSE 
    INSERT INTO `users_remark` SET `remark` = 'testing123', `user_id`=1, `remark_user_id` = 3 

Answer 1

這裏是既INSERT和UPDATE條款（T-SQL語法查詢）：

IF [condition here] BEGIN 
    UPDATE `users_remark` 
    SET `remark` = 'testing123' 
    WHERE `user_id`=1 
     AND `remark_user_id` = 3 
END 
ELSE BEGIN 
    INSERT INTO `users_remark` (`user_id`, `remark_user_id`, `remark`) 
    VALUES (1, 3, 'testing123) 
END 

編輯：MySQL的句法

DECLARE @numrecords INT 

SELECT @numrecords = count(*) 
FROM `users_remark` 
WHERE `user_id` = 1 
    AND `remark_user_id` = 3 

IF @numrecords > 0 THEN 
    UPDATE `users_remark` 
    SET `remark` = 'testing123' 
    WHERE `user_id`=1 
     AND `remark_user_id` = 3 
ELSE 
    INSERT INTO `users_remark` (`user_id`, `remark_user_id`, `remark`) 
    VALUES (1, 3, 'testing123) 
END IF 

希望這將幫助你相同的查詢。

Answer 2

我終於嘗試將代碼放到php中，它工作並且更容易理解。

 $checkRemark = mysqli_query($GLOBALS['db_conn'], "SELECT * FROM `users_remark` WHERE `user_id`=".$data['uid']." AND `remark_user_id` = ".$data['ruid']); 
     if (mysqli_num_rows($checkRemark)>0){ 
      $remarkSql = "UPDATE `users_remark` 
         SET `remark` = '".$data['remark']."' 
         WHERE `user_id`=".$data['uid']." 
          AND `remark_user_id` = ".$data['ruid']; 
     } else { 
      $remarkSql = "INSERT INTO `users_remark` (`user_id`, `remark_user_id`, `remark`) 
          VALUES (".$data['uid'].", ".$data['ruid'].", '".$data['remark']."')"; 
     }