如何使用SQLSTATE'；45000'；PHP中的消息文本？

我有这样一个触发器：

CREATE TRIGGER prevent_self_votes BEFORE INSERT ON votes
  FOR EACH ROW
    BEGIN
      IF(new.user_id = (SELECT author_id FROM posts WHERE id=new.post_id)) THEN
        SIGNAL SQLSTATE '45000' SET MESSAGE_TEXT = "you cannot vote for yourself";
      END IF;
    END;

现在我想知道，我如何使用PHP中的文本

您不能为自己投票

---

注意：我使用PDO。

如果您的查询失败，请检查导致失败的原因，查看的定义

您可以执行try…catch并检查语句执行的结果，以打印如下错误信息：

CREATE TRIGGER prevent_self_votes BEFORE INSERT ON votes
  FOR EACH ROW
    BEGIN
      IF(new.user_id = (SELECT author_id FROM posts WHERE id=new.post_id)) THEN
        SIGNAL SQLSTATE '45000' SET MESSAGE_TEXT = "you cannot vote for yourself";
      END IF;
    END;

存根

create table votes (user_id int);

delimiter //

create trigger prevent_self_votes before insert on votes
for each row
begin
    if (new.user_id = 12) then
        signal sqlstate '45000' set message_text = 'You cannot vote for yourself, dude!';
    end if;
end //

delimiter ;

PHP脚本

<?php

$db = new PDO('mysql:host=localhost;dbname=test', 'test', 'test');
$sql = 'insert into votes values (:user_id)';
$statement = $db->prepare($sql);
if ($statement === false) {
    echo 'statement is false';
    exit();
}

try {
    $result = $statement->execute(array(':user_id'=>12));
    if ($result === false) {
        $error = $statement->errorInfo();
        print_r($error);
        echo "$error[2] ... is the error reported by trigger\n";
    }
    else {
        print_r($result);
        echo 'Inserted', "\n";
    }
}
catch (PDOException $e) {
    echo $e->getMessage();
}

?>

$ php test.php
Array
(
    [0] => 45000
    [1] => 1644
    [2] => You cannot vote for yourself, dude!
)
You cannot vote for yourself, dude! ... is the error reported by trigger

正如您在这里注意到的，您可以使用

$statement->errorInfo（）[2]

的输出来提取触发器提供的信息

表示数组中的第一项是SQLSTATE ANSI SQL错误代码，第二项是特定于驱动程序的错误代码，第三项是特定于驱动程序的错误消息