SQL中的語法錯誤PHP

Question

我試圖將列的列設置爲每行中的字符串（如果該列存在）。不過，我收到SQL語法錯誤，無法查明究竟是什麼的問題是：

while($db = mysqli_fetch_array(mysqli_query($conn, "SHOW DATABASES"))){ 
    $id = $db['id']; 

    $sql = /** @lang text */ 
      "SELECT IF(EXISTS(
        SELECT DISTINCT `info` 
         FROM INFORMATION_SCHEMA.COLUMNS 
         WHERE COLUMN_NAME IN ('borrower') 
          AND TABLE_SCHEMA = '$db')) 
        BEGIN 
         UPDATE `info` 
          SET `borrower` = '****' 
          WHERE `id` = '$id' 
        END"; 

    $query = mysqli_query($conn, $sql); 

    if (!$query){ 
     // Deal with error 
    } 
} 

的語法錯誤，我收到回：

information_schema
db1
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 ')
BEGIN
UPDATE info
SET borrower = '****'
' at line 5

我知道那一定是一件很渺小，但我已經卡住了一段時間，似乎無法找到我的錯誤。

Answer 1

試試這個語法的查詢 -

IF EXISTS (SELECT DISTINCT `info` 
        FROM INFORMATION_SCHEMA.COLUMNS 
        WHERE COLUMN_NAME IN ('borrower') 
         AND TABLE_SCHEMA = '$db')) THEN 
    UPDATE `info` 
         SET `borrower` = '****' 
         WHERE `id` = '$id' 


    END IF; 

我在if條件的結束和End if，而不是隻if添加Then，和我刪除了select來。你想要選擇什麼？它只是更新條款。

更新從here

you can't use it like a normal query. Control structures like IF or WHILE are only allowed in stored procedures or functions.

MYSQL面板

delimiter $$ 
create procedure YourIfConditionSP() 
begin 
    IF EXISTS (SELECT DISTINCT `info` 
        FROM INFORMATION_SCHEMA.COLUMNS 
        WHERE COLUMN_NAME IN ('borrower') 
         AND TABLE_SCHEMA = '$db') THEN 
    UPDATE `info` 
         SET `borrower` = '****' 
         WHERE `id` = '$id'; 


    END IF; 
end $$ 
delimiter ; 

例子，你必須改變你的PHP代碼調用存儲過程。

PHP

//run the stored procedure 
$result = mysqli_query($connection, 
     "CALL YourIfConditionSP") or die("Query fail: " . mysqli_error()); 

How to call a MySQL stored procedure from within PHP code?