PHP的约束冲突错误1452

Question

早上好， 我有难同当I，M试图在我的数据库与这个PDO插入事件此SQL错误的一个大问题：

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SQL：

$subsquery1 = "SELECT cat_id FROM categories WHERE cat_name = ".$event_cat; 

$subsquery2 = "SELECT tournament_id FROM tournaments WHERE tournament_name = ".$event_tournament; 

$sqlx = "INSERT INTO events(event_team1, event_team2, event_cat, event_tournament, event_start_at, event_end_to, event_by) VALUES(:event_team1, :event_team2, :event_cat, :event_tournament, :event_start_at, :event_end_to, :event_by)"; 

// Prepare statement 
$statementx = $pdo->prepare($sqlx); 

// execute the query 
$resultx = $statementx->execute(array(':event_team1' => $event_team1, ':event_team2' => $event_team2, ':event_cat'=> $subsquery1, ':event_tournament'=> $subsquery2, ':event_start_at' => $event_start_at, ':event_end_to' => $event_end_to,':event_by'=>$event_by)); 

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SQL错误，请：

完整性约束违规：1452不能添加或更新一个孩子 行：外键约束失败（datenbankevents，约束 events_ibfk_1外键（event_cat）参考文献categories （cat_id）ON DELETE CASCADE ON UPDATE CASCADE）

-- Table structure for table `events` 
CREATE TABLE `events` (
    `event_id` int(8) NOT NULL AUTO_INCREMENT PRIMARY KEY, 
    `event_team1` varchar(255) NOT NULL, 
    `event_team2` varchar(255) NOT NULL, 
    `event_start_at` timestamp NOT NULL, 
    `event_end_to` timestamp NOT NULL, 
    `event_cat` int(8) NOT NULL, 
    `event_by` int(8) NOT NULL, 
    `event_tournament` int(8) NOT NULL, 
    KEY `event_cat` (`event_cat`), 
    KEY `event_by` (`event_by`), 
    KEY `event_tournament` (`event_tournament`) 
)ENGINE=InnoDB DEFAULT CHARSET=latin1; 

- 对表的约束posts

​​

- 约束的表events

ALTER TABLE `events` ADD CONSTRAINT `events_ibfk_1` FOREIGN KEY (`event_cat`) REFERENCES `categories` (`cat_id`) ON DELETE CASCADE ON UPDATE CASCADE, 
ADD CONSTRAINT `events_ibfk_2` FOREIGN KEY (`event_by`) REFERENCES `users` (`id`) ON UPDATE CASCADE, 
    ADD CONSTRAINT `events_ibfk_3` FOREIGN KEY (`event_tournament`) REFERENCES `tournaments` (`tournament_id`) ON DELETE CASCADE ON UPDATE CASCADE; 

请有人能有助于...

Answer 1

完整性约束违规：1452不能添加或更新子行： 一个外键约束失败（datenbank.events， CONSTRAINTevents_ibfk_1FOREIGN KEY（event_cat） REFERENCEScategories（ cat_id）

您正在对表events执行插入操作，并将值放在列event_cat中。

该值尚不表categories列cat_id存在。

而你说过它必须。所以数据库引擎说它不会这样做。它忠实地遵守你的命令。