We want to list the basic situation of each student with the STUDENT table, if a student is not elected, only the basic situation information is output. This is the standard external connection (OUT JOIN): The instance code is as follows:
Select Student.sno, Sname, Ssex, Sage, Sdept, CNO, GRADE
From student, sc
Where student.sno = sc.SNO (*);
The representation of the outer connection is to add symbols * (some database system ) in connection. The external connection is like the room to add an universal row while the room is.
