SQL/ SEARCHING 按ClassId查询

Posted 2022-07-20 gamecenter

 ST_NAME  || ST_ID  || CLASS_ID  || CLASS_INFO   
 ---------------------------------------------  
  MARK     ||   1    ||     100   || MATH  
  YEN      ||   2    ||     101   || CHEM  
  SALLY    ||   3    ||     100   || MATH  
  SARA     ||   4    ||     103   || HIST  
正确解法：

create table test(st_name varchar, st_id int, class_id int, class_info int);

insert into test values(‘MARK‘, 1, 100, ‘MATH‘);
insert into test values(‘YEN‘, 2, 101, ‘CHEM‘);
insert into test values(‘MARK‘, 3, 100, ‘MATH‘);
insert into test values(‘MARK‘, 4, 103, ‘HOST‘);

SELECT (MAX(counter) > 1) as sameClass FROM (SELECT COUNT(st_id) counter FROM test 
WHERE ST_ID IN (1,2) GROUP BY class_info);

SELECT (MAX(counter) > 1) as sameClass FROM (SELECT COUNT(st_id) counter FROM test 
WHERE ST_ID IN (1,2,3) GROUP BY class_info);