sql中inner jion,left jion,right jion 的使用

現有兩張表

inner jion -內連接(完全匹配)

SELECT * FROM dbo.UserInfo u  INNER JOIN dbo.Student s on  u.StudentID=s.StudentName

left jion 左連接(以左表爲準,如果右表匹配不到則會賦值爲空)

SELECT * FROM dbo.UserInfo u LEFT JOIN dbo.Student s ON u.StudentID=s.StudentName

right jion 右連接(和left jion相反，以右表爲準,如果左邊記錄不存在,則賦值爲空)

SELECT * FROM dbo.UserInfo u right JOIN dbo.Student s ON u.StudentID=s.StudentName