增删改与事务

增删改与事务要点

• INSERT 用预处理防注入，执行成功即入库
• UPDATE 必须带 WHERE，漏写会改光整表
• DELETE 同样带 WHERE，误删只能靠备份还原
• mysqli_begin_transaction 开事务，成对 commit 提交
• 中途异常走 mysqli_rollback 回滚，保护数据一致
• 操作完统一 mysqli_close 收尾，别留悬挂连接

增删改与事务示例

						$conn = mysqli_connect("127.0.0.1", "app_user", "app_pass", "shop_db");

						// 新增
						$stmt = mysqli_prepare($conn, "INSERT INTO product (name, price) VALUES (?, ?)");
						mysqli_stmt_bind_param($stmt, "sd", $name, $price);
						$name = "机械键盘"; $price = 299.00;
						mysqli_stmt_execute($stmt);

						// 更新与删除
						mysqli_query($conn, "UPDATE product SET price = 259.00 WHERE id = 1");
						mysqli_query($conn, "DELETE FROM product WHERE id = 99");

						// 事务
						mysqli_begin_transaction($conn);
						try {
						    mysqli_query($conn, "UPDATE account SET balance = balance - 100 WHERE id = 1");
						    mysqli_query($conn, "UPDATE account SET balance = balance + 100 WHERE id = 2");
						    mysqli_commit($conn);
						} catch (Exception $e) {
						    mysqli_rollback($conn);
						}
						mysqli_close($conn);

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