在子查詢中選擇所有EXCEPT結果

Question

我有一個連接多個表（3或4）的查詢並按預期得到結果。

SELECT DISTINCT test_title, stt_id FROM student_tests 
LEFT JOIN student_test_answers ON sta_stt_num = stt_id 
JOIN tests ON stt_test_id = test_id 
WHERE student_test_answer_id IS NULL 

我有另外一個查詢，顯示另一組數據，它基本上是這樣的：

SELECT test_id, COUNT(*) AS theCount FROM tests 
    JOIN test_questions ON test_id= tq_test_id 
    WHERE type= 'THE_TYPE' 
    GROUP BY test_id 
    HAVING theCount = 1 

所以基本上我想不包括第一個第二個查詢的結果。 test_id將是連接字段。

我試過了WHERE NOT EXISTS（ - 上面的查詢 - ）但是沒有返回任何不正確的結果。我也試過'NOT IN（）'

有沒有更好的方法來做到這一點？

Answer 1

嘗試這樣：

(SELECT test_id, COUNT(*) AS theCount FROM tests 
JOIN test_questions ON test_id= tq_test_id 
WHERE type= 'THE_TYPE' 
GROUP BY test_id 
HAVING theCount = 1) outer 
LEFT JOIN (
     [OtherQuery] 
) a ON outer.test_id = a.test_id 
WHERE a.test_id IS NULL 

Answer 2

到底是什麼第二個查詢？我只在這裏看到一個查詢，並且沒有子查詢。另外，精確模式的sqlfiddle會很有幫助。

無論如何，我想你想要某種排除連接。它看起來是這樣的：

select  test.test_id, count(*) as theCount 
from  tests test 
join  test_questions tq 
on   tq.test_id = test.test_id 
left join tests excluded_test 
on   excluded_test.test_id = test.test_id 
where  tq.type = 'THE_TYPE' 
and  << Some condition that explains what excluded_test is >> 
and  excluded_test.test_id is null 

編輯：是啊，肯定有很多細節，從原來的問題失蹤（其中有在某些方面被修補），以及這些人仍下落不明。知道你的例子的完整表格結構很重要，所以很難提供一個好的具體答案。

Answer 3

寫在評論你應該能夠做到這一點是這樣的：

SELECT 
    DISTINCT test_title, 
    olc_stt_i_num 
FROM 
    student_tests 
LEFT JOIN 
    student_test_answers 
     ON olc_sta_i_stt_num = olc_stt_i_num 
INNER JOIN 
    ol_class_tests 
     ON stt_test_num = test_num 
WHERE 
    student_test_answer_id IS NULL 

    -- added this: replace test_id with real column 
    AND ***test_id*** NOT IN (
     SELECT 
     test_id 
     FROM 
     tests  
     JOIN 
     test_questions 
      ON test_id= tq_test_id  
     WHERE 
     type= 'THE_TYPE'  
     GROUP BY 
     test_id  
     HAVING 
     COUNT(*) = 1 
    ) 

Answer 4

這裏就是我的回答。左外連接爲您提供參與者（測試）。如果test_questions中沒有匹配，則它將返回測試行，但對於test_questions則爲null。因此，如果您查找任何空的test_question.test_id，您將得到您正在查找的內容。

我也會在你的count子句中具體說明，而不是爲了確保mysql知道你真正想要計數的數值（*）。

create database test; 
use test; 

create table test 
(
    test_id int, 
    `the_type` varchar(20) 
); 

create table test_questions 
(
    test_question_id int, 
    test_id int, 
    `the_type` varchar(20) 
); 

insert into test values (1, 'history'); 
insert into test values (2, 'chemistry'); 
insert into test values (3, 'reading'); 

insert into test_questions values (1, 1, 'hard question'); 
insert into test_questions values (2, 1, 'medium question'); 
insert into test_questions values (3, 2, 'hard question'); 
insert into test_questions values (4, 2, 'easy question'); 

select * from test; 
select * from test_questions; 

select t.test_id, count(distinct t.test_id) 
from test t 
left outer join test_questions tq on tq.test_id = t.test_id 
where 
    tq.test_id is null 
group by 
    t.test_id