Mysql中表student_table(id,name,birth,sex),插入如下记录:
('1001' , '' , '2000-01-01' , '男');
('1004' , '张三' , '2000-08-06' , '男');
('1005' , NULL , '2001-12-01' , '女');
('1004' , '张三' , '2000-08-06' , '男');
('1005' , NULL , '2001-12-01' , '女');
('1006' , '张三' , '2001-12-02' , '女');
执行 select t1.name from
(select * from student_table where sex = '女')t1 left join
(select * from student_table where sex = '男')t2
on t1.name = t2.name;
的结果行数是()?