Question

示例数据：

event_id, session_id, did_tap_on_screen
1         1           true
2         1           false
3         2           false
4         2           false

期望的结果：

session_id, did_tap_on_screen
1           true
2           false

基本上，我希望按session_id进行分组，如果any为true则返回true，如果全部为假则返回false

这是我写的伪查询：

SELECT
  session_id,
  did_tap_on_screen -- what should I do here
FROM events
GROUP BY session_id

Answer 1

如果did_tap_on_screen是一个字符串，您可以这样做：

select session_id, max(did_tap_on_screen)
from events
group by session_id;

如果它是布尔值（某种类型），则适当的公式取决于数据库。例如，Postgres支持bool_or()

select session_id, bool_or(did_tap_on_screen)
from events
group by session_id;

Answer 2

以下是确定每import UIKit class CustomTableViewCell: UITableViewCell, UITextFieldDelegate { @IBOutlet weak var inputLabel: UILabel! @IBOutlet weak var inputText: UITextField! @IBOutlet weak var labelLabel: UILabel! @IBOutlet weak var labelDetail: UILabel! @IBOutlet weak var picker: UIPickerView! @IBOutlet weak var largeInputText: UITextField! override func awakeFromNib() { super.awakeFromNib() // Initialization code inputText.delegate = self } func textFieldShouldReturn(textField: UITextField) -> Bool { print("return button in CustomTableViewCell") inputText.resignFirstResponder() return true } override func setSelected(selected: Bool, animated: Bool) { super.setSelected(selected, animated: animated) // Configure the view for the selected state } }个did_tap_on_screen是否为真的方法：

session_id

如何按一列分组并为另一列返回ifnull

2 个答案: