Question

我需要交叉引用行。如果该行不存在，则将其插入。

在将其插入数据库之前，需要满足以下条件：

首先找到属于用户（user_id）的约会。

然后查找与约会ID（appointment_id）相匹配的约会。如果约会ID不存在，请继续执行下一步。

如果约会ID不存在，则搜索约会是否与约会日期和时间（appointment_date）（appointment_time）相匹配。

如果不存在，则INSERT进入数据库。

到目前为止，这是我的代码。如何使SELECT的嵌套if语句更快，更简单？

// Search for appointment by appointment ID to see if it already exists
$stmt = $dbh->prepare("SELECT id FROM users WHERE user_id = :user_id AND appointment_id = :appointment_id LIMIT 1");
$stmt->bindParam(':user_id', $userId);
$stmt->bindParam(':appointment_id', $appointmentId);
$stmt->execute();
$result = $stmt->fetch(PDO::FETCH_ASSOC);

// If appointment does not already exist, search for appointment by date and time
if(!$result) {
    $stmt = $dbh->prepare("SELECT id FROM users WHERE user_id = :user_id AND appointment_date = :appointment_date AND appointment_time = :appointment_time LIMIT 1");
    $stmt->bindParam(':user_id', $userId);
    $stmt->bindParam(':appointment_date', $appointmentDate);
    $stmt->bindParam(':appointment_time', $appointmentTime);
    $stmt->execute();
    $result2 = $stmt->fetch(PDO::FETCH_ASSOC);

    if(!$result2) {
        // If appointment does not already exist, insert into database:
        $stmt = $dbh->prepare("INSERT INTO...")
    }
}

我怎样才能使它变得更快，更简单/更短？

Answer 1

如果您不需要区分两个查询，只需结合您的条件即可：

SELECT id FROM users WHERE user_id = :user_id AND 
 (appointment_id = :appointment_id OR 
  appointment_date = :appointment_date AND appointment_time = :appointment_time)
LIMIT 1

Answer 2

我认为您可以尝试使用UNION来仅执行一个查询并使用一半代码。

// Search for appointment by appointment ID to see if it already exists
$stmt = $dbh->prepare("(SELECT id FROM users WHERE user_id = :user_id AND appointment_id = :appointment_id) UNION (SELECT id FROM users WHERE user_id = :user_id AND appointment_date = :appointment_date AND appointment_time = :appointment_time) LIMIT 1");
$stmt->bindParam(':user_id', $userId);
$stmt->bindParam(':appointment_id', $appointmentId);
$stmt->bindParam(':appointment_date', $appointmentDate);
$stmt->bindParam(':appointment_time', $appointmentTime);
$stmt->execute();
$result = $stmt->fetch(PDO::FETCH_ASSOC);

// If appointment does not already exist, search for appointment by date and time
if(!$result) {
    $stmt = $dbh->prepare("INSERT INTO...")
}

我上面没有真正测试过此代码。可能需要一些调整。

告诉我如果事情太糟了。

在PHP MySQL SELECT中嵌套if语句

2 个答案: