如何从上课的学生那里获得主题仅为“数学和科学”的独特学生证

Question

表

+------+-----------+
| ID   | subject   |
+------+-----------+
|    1 | science   |
|    1 | maths     |
|    2 | maths     |
|    3 | science   |
|    4 | science   |
|    4 | biology   |
|    4 | maths     |
|    5 | biology   |
|    5 | economics |
+------+-----------+
9 rows in set (0.00 sec)

上表要查询以科目和科学为主题的唯一ID

Answer 1

您可以在下面尝试-

select distinct id
from tablename
where subject in ('science', 'maths')
having count(distinct subject)=2

Answer 2

您在这里：

SELECT 
  DISTINCT(`ID`)
FROM 
  `TABLE` 
WHERE 
  `subject` IN ('science', 'maths');

已更新：

CREATE TABLE test (
  id INT  ,
  subject varchar(30)
);

INSERT INTO test (id, subject) VALUES 
(1,'science'),
(1,'maths'),
(2,'maths'),
(3,'science'),
(4,'science'),
(4,'biology'),
(4,'maths'),
(5,'biology'),
(5,'economics');

SELECT
  DISTINCT(a.id)
FROM 
  test a
  LEFT JOIN test b on b.id=a.id  AND b.subject IN ('science', 'maths')
WHERE 
  a.subject='science' AND b.subject='maths';
/*output: 1, 4*/

希望这会有所帮助