Question

我生成了下表：

CREATE table user (  
    user_id INT NOT NULL UNIQUE AUTO_INCREMENT,  
    user_phone_number INT,  
    user_city VARCHAR(32) NOT NULL,  
    PRIMARY KEY (user_id)
);

我被问到以下内容：每个电话号码长度的用户数量（数字位数）

我尝试以下方法：

SELECT LENGTH(user_phone_number)
FROM user
WHERE user is not null
GROUP BY user_phone_number);

但如果有多个用户具有相同的电话号码长度，则会在多行中重复这些用户，而不是提供每长度的总计。请帮忙

Answer 1

您的SQL有两个问题。最明显的是你遗漏了SELECT。如果你想数点什么，这很重要。

第二个是GROUP BY列和SELECT LENGTH(user_phone_number), COUNT(*) FROM user WHERE user_phone_number is not null GROUP BY LENGTH(user_phone_number);列不匹配。这些应该（几乎总是）相同：

ORDER BY LENGTH(user_phone_number)

最后你可能想要func hideButton() { UIView.animate(withDuration: 0.2, delay: 0, animations: { self.MainButton.alpha = 0 }, completion: { finished in self.MainButton.isHidden = true }) Timer.scheduledTimer(timeInterval: 1.2, target: self, selector: #selector(GameViewController.ShowButton), userInfo: nil, repeats: false) } func showButton() { self.MainButton.isHidden = false UIView.animate(withDuration: 0.2, delay: 0, animations: { self.MainButton.alpha = 1 }, completion: { finished in }) Timer.scheduledTimer(timeInterval: 1.2, target: self, selector: #selector(GameViewController.HideButton), userInfo: nil, repeats: false) }。

计算每行每列的数字长度

1 个答案: