Postgresqlの句は、と私は私のクエリに特定の条件のために参加を追加しようとしています

Question

参加する場所の条件：

select * 
from (
    select 
     row_number() over (partition by dl.value order by random()) as rn, 
     dl.value, 
     q.question_text, q.option_a, q.option_b, q.option_c, q.option_d, 
     q.correct_answer, q.image_link, q.question_type 
    from 
     questions_bank q 
     inner join 
     sports_type st on st.id = q.sports_type_id 
     inner join 
     difficulty_level dl on dl.id = q.difficulty_level_id 
    where st.game_type = lower('cricket') and dl.value in ('E','M','H') 
) s 
where 
    value = 'E' and rn <= 7 or 
    value = 'M' and rn <= 4 or 
    value = 'H' and rn = 1 

だから、もし値=「E」、これらの質問の50％を（7） '一般的な'質問カテゴリからのものでなければなりません。

他の値（M/H）については、 "case when dl.value='E' then rn=4 (50% of 7) from question_category='general', 3 (7-4) else 7 end"

ような何か（私はINNER JOIN question_category qc ON qc.id = q.question_category_idのように参加を追加する必要があります）

に、いずれかがquestion_category

参照してくださいとそこに参加すべきではありません元の質問を表示するにはquestion

UPDATE：

私がやろうとしています：

select *               
    from (
      select 
       row_number() over (partition by dl.value order by random()) as rn, 
       row_number() over (partition by dl.value, LOWER(qc.value) = LOWER('general') order by random()) as rnc, 
       dl.value, qc.value as question_category, 
       q.question_text, q.option_a, q.option_b, q.option_c, q.option_d, 
       q.correct_answer, q.image_link, q.question_type 
      from 
       questions_bank q 
       inner join 
       question_category qc on qc.id = q.question_category_id 
       inner join 
       sports_type st on st.id = q.sports_type_id 
       inner join 
       difficulty_level dl on dl.id = q.difficulty_level_id 
      where st.game_type = lower('cricket') and dl.value in ('E','M','H') 
     ) s 
    where 
     (value = 'E' and rnc <= 4) or (value = 'E' and rn <= 3)or 
     value = 'M' and rn <= 3 or 
     value = 'H' and rn <= 2; 

が、これは値= 'E' のための余分な行を返しています。 （rncから4つ、value = 'E'のときrnから4）。私は何が欠けていますか？

Answer 1

SELECT * 
FROM (
    SELECT 
     row_number() over (partition by dl.value order by random()) as rn 
     , dl.value 
     , q.question_text, q.option_a, q.option_b, q.option_c, q.option_d 
     , q.correct_answer, q.image_link, q.question_type 
    FROM 
     questions_bank q 
     JOIN sports_type st ON st.id = q.sports_type_id 
     JOIN difficulty_level dl ON dl.id = q.difficulty_level_id 
    WHERE st.game_type = lower('cricket') AND dl.value IN ('E','M','H') 
    AND (dl.value = 'E' -- No extra condition for 'E' 
     OR EXISTS   -- Extra condition for non-'E' 
      (SELECT * FROM question_category qc 
      WHERE qc.id = q.question_category_id 
     ) 
     ) 
) s 
WHERE value = 'E' AND rn <= 7 
    or value = 'M' AND rn <= 4 
    or value = 'H' AND rn = 1 
     ; 

Answer 2

カテゴリには、1というIDを付けました。必要に応じて交換してください。

select * 
from (
    select 
     row_number() over (partition by dl.value order by random()) as rn, 
     row_number() over (
      partition by dl.value, question_category_id = 1 
      order by random() 
     ) as rnc, 
     dl.value, 
     q.question_text, q.option_a, q.option_b, q.option_c, q.option_d, 
     q.correct_answer, q.image_link, q.question_type 
    from 
     questions_bank q 
     inner join 
     sports_type st on st.id = q.sports_type_id 
     inner join 
     difficulty_level dl on dl.id = q.difficulty_level_id 
     inner join 
     question_category qc on qc.id = q.question_category_id 
    where st.game_type = lower('cricket') and dl.value in ('E','M','H') 
) s 
where 
    value = 'E' and rn <= 4 or 
    value = 'M' and rnc <= 4 or 
    value = 'H' and rn = 1 

Answer 3

私は私が思いついたものです以下、

をする方法を見つけ出すことができます。 dl.value = 'E'、RNはわずか7でなければなりません

select * 
       from (
        select 
         row_number() over (partition by dl.value order by random()) as rn, 
         row_number() over (partition by dl.value, LOWER(qc.value) = LOWER('general') order by random()) as rnc, 
         row_number() over (partition by dl.value, LOWER(qc.value) != LOWER('general') order by random()) as rnq, 
         dl.value, qc.value as question_category, 
         q.question_text, q.option_a, q.option_b, q.option_c, q.option_d, 
         q.correct_answer, q.image_link, q.question_type 
        from 
         questions_bank q 
         inner join 
         question_category qc on qc.id = q.question_category_id 
         inner join 
         sports_type st on st.id = q.sports_type_id 
         inner join 
         difficulty_level dl on dl.id = q.difficulty_level_id 
        where st.game_type = lower('cricket') and dl.value in ('E','M','H') 
       ) s 
       where 
        (value = 'E' and rnq <= 4 and LOWER(question_category) != LOWER('general')) or 
        (value = 'E' and rnc <= 3 and LOWER(question_category) = LOWER('general')) or 
        value = 'M' and rn <= 3 or 
        value = 'H' and rn <= 2