create table teacher
(
tid varchar(12) not null,
tname varchar(20) not null,
constraint PK_TEACHER primary key (tid)
)
go
create table student
(
xh varchar(20) not null,
tid varchar(12) null ,
sname varchar(20) not null,
constraint PK_STUDENT primary key (xh)
)
go
create index Relation_11_FK on student (tid)
go
alter table student
add constraint FK_STUDENT_RELATION__TEACHER foreign key (tid)
references teacher (tid)
go
如上,我有两个表,teacher和student.我想用left join查出一个老师下有多少个学生.
如:select teacher.* , student.* from teacher left join student on teacher.tid = student.tid;
但是我想再加上一个条件在后面,如是id为'0001'的老师所带的学生,应该怎么加?
我直接在后面加上..from teacher left join student on teacher.tid = student.tid and teacher.tid = '001'没有任何效果, 它还是会将所有老师的全查出来??
