在MySQL中按条件分组

Question

我有一个mysql查询，我需要在Group by语句中添加一些条件，如果我在Group by中使用单个字段，但我需要在Group by中包含两个字段，这是我的查询中的任何一个，请帮助我找出答案问题

SELECT (CASE 
                WHEN CSR.skill_type = 1 THEN 
                    (SELECT skills_value from cv_skills 
                    WHERE skills_id = CSR.skill_id )
                WHEN CSR.skill_type = 2 THEN 
                    (SELECT ostype_name from  cv_os_type 
                    WHERE ostype_id = CSR.skill_id )
                WHEN CSR.skill_type = 3 THEN 
                    (SELECT dbtype_name from cv_db_type 
                    WHERE dbtype_id = CSR.skill_id)
                WHEN CSR.skill_type = 4 THEN 
                    (SELECT title from candidate_competencies 
                    WHERE id = CSR.skill_id)    
                WHEN CSR.skill_type = 0 THEN 
                    IT.type_name
            END) AS skill_name,
            (CASE 
                WHEN IT.type_parent_id > 0 THEN
                    IT.type_parent_id
                WHEN IT.type_parent_id = 0 THEN
                     CIS.interview_type
            END) AS typeId,
            (CASE 
                WHEN CSR.skill_type = 4 THEN 
                    minimum_rating 
            END) AS minimum_rating,
             AVG( CSR.rate ) AS skill_rating,
                                CSR.skill_type,CIS.created, CC.id
FROM `candidate_interview_skill_rate` `CSR`
LEFT JOIN `candidate_interview_process` `CIP` ON CSR.interview_process_id = CIP.id
LEFT JOIN `candidate_interview_schedule` `CIS` ON CIS.id = CIP.interview_schedules_id AND CIS.archive_date IS NULL
LEFT JOIN `candidate_interview` `CI` ON CI.id = CIS.interview_id AND CI.archived_date IS NULL
LEFT JOIN `interview_type` `IT` ON IT.id = CIS.interview_type
LEFT JOIN `candidate_competencies` `CC` ON CC.id = CSR.skill_id
WHERE CI.candidate_user_id = 39
GROUP BY (CASE
         WHEN CSR.skill_type > 0 THEN
           CSR.skill_id, CSR.skill_type
         ELSE CIS.interview_type
     END)
ORDER BY `CSR`.`skill_type`

Answer 1

您可以将CSR.skill_id，CSR.skill_type连接到单个列，并在select语句中使用它。 分组者需要像这样

GROUP BY  CASE
    WHEN CSR.skill_type > 0  THEN
            CONCAT(CSR.skill_id, '-', CSR.skill_type)
    ELSE 
            CIS.interview_type
    END;

希望这行得通。

Answer 2

您可以在GROUP BY子句中包含多个表达式，就像用SELECT列表一样，用逗号分隔表达式即可。

SELECT列表中的表达式通常在GROUP BY子句中重复。

通常可以使用CASE表达式来支持更复杂的条件集。

很难为您的查询，缺少样本数据和所需的输出提供更具体的帮助。