在SQL中可能吗？ moodle

Question

你好，我正在Moodle中做一个项目，并且有一个疑问是否可以实现。我已经尝试将这3个查询合并为一个。

    select c.fullname, count(1) as total from {role_assignments} ra INNER JOIN 
    {logstore_standard_log}  as lsl ON ra.userid = lsl.userid  
    INNER JOIN {course} as c on lsl.courseid =c.id 
    WHERE  lsl.action="viewed" and lsl.target = "course" GROUP BY c.fullname



       select c.fullname, count(1) as student from {role_assignments} ra INNER JOIN 
       {logstore_standard_log}  as lsl ON ra.userid = lsl.userid  
       INNER JOIN {course} as c on lsl.courseid =c.id 
       WHERE ra.roleid=5 AND lsl.action="viewed" and lsl.target = "course" GROUP BY c.fullname


   select c.fullname, count(1) as rest from {role_assignments} ra INNER JOIN 
   {logstore_standard_log}  as lsl ON ra.userid = lsl.userid  
   INNER JOIN {course} as c on lsl.courseid =c.id 
   WHERE ra.roleid!=5 AND lsl.action="viewed" and lsl.target = "course" GROUP BY c.fullname

从我所看到的来看，这可能可以通过子查询来完成，但是我似乎找不到解决方法。

感谢您的帮助

Answer 1

select c.fullname, count(1) as total, NULL as student, null as rest from {role_assignments} ra INNER JOIN 
{logstore_standard_log}  as lsl ON ra.userid = lsl.userid  
INNER JOIN {course} as c on lsl.courseid =c.id 
WHERE  lsl.action="viewed" and lsl.target = "course" GROUP BY c.fullname

UNION

select c.fullname, null, count(1) as student, null from {role_assignments} ra INNER JOIN 
{logstore_standard_log}  as lsl ON ra.userid = lsl.userid  
INNER JOIN {course} as c on lsl.courseid =c.id 
WHERE ra.roleid=5 AND lsl.action="viewed" and lsl.target = "course" GROUP BY 
  c.fullname

UNION

select c.fullname, null, null, count(1) as rest from {role_assignments} ra INNER JOIN 
{logstore_standard_log}  as lsl ON ra.userid = lsl.userid  
INNER JOIN {course} as c on lsl.courseid =c.id 
WHERE ra.roleid!=5 AND lsl.action="viewed" and lsl.target = "course" GROUP BY    
 c.fullname

PS：注意select部分