员工:一张我所有员工的桌子
团队:创建了团队的表格
team_employees::具有团队与员工列表的关系的表。
因此,基本上,我需要在团队中选择所有没有团队的员工。例如,如果您看到在表team_employees中,id_team#2没有id_employee#2。我要查找的查询选择应该给我ID员工#2(但只给ID#2的团队)
我已经尝试过像这样LEFT JOIN
,但是没有运气,因为我认为这会在team_id字段中给我一个NULL,但不是:
SELECT te.id_team AS id_team, e.id, e.name
FROM employees e
LEFT JOIN team_employees te
ON te.id_employee = e.id
WHERE id_team = 2
GROUP BY e.id
感谢您的帮助!
答案 0 :(得分:2)
使用这种形式的左联接
System.loadLibrary(Core.NATIVE_LIBRARY_NAME);
VideoCapture VC = new VideoCapture(0);
//First you requried open Camera.
VC.open();
//Now for geting 'Frame per secand"
VC.get(Videoio.CAP_PROP_FPS); // it returns FPS(Frame per secand)
//Now for seting 'Frame per secand"
VC.set(Videoio.CAP_PROP_FPS,10.0);//in this 10.0 is value for FPS,its double value.
VC.relase();
有时称为“左除联接”。您需要做的是将SELECT te.id_team AS id_team, e.id, e.name
FROM employees e
LEFT JOIN team_employees te ON te.id_employee = e.id AND te.id_team = 2
WHERE te.id_team IS NULL
放入连接条件中,而不是where子句中。然后使用where子句查找与team表不匹配的所有行。
替代:
e.id_team = 2