从两个表中选择多个列，其中一个表的一列具有多个 where 条件，并将它们按两列分组并按一排序

Question

我有两个表，分别是“appointment”和“skills_data”。

约会表的结构是：

id_ap || ap_meet_date || id_skill || ap_status. 

而ap_status的值有complete、confirm、cancel和miss。

而技能数据表包含两列，即：

id_skill || skill

我想获取每个条件的约会总数

ap_status = ('complete' and 'confirm'), 
ap_status = 'cancel' and 
ap_status = 'missed' 

GROUP BY id_skill and year and 
order by year DESC

我尝试了这个查询，它只计算了一个条件，但我想根据前面提到的 group by 和 order by 子句获得另外两个条件。

如果没有符合特定条件的记录（例如：某项技能2018年缺约0次），则应显示输出值为0表示零计数。

有人可以向我建议我是否应该实施多选查询或 CASE 子句来实现我的预期结果。我在约会表中有很多记录，并且想要一种有效的方式来查询我的记录。谢谢！

SELECT a.id_skill, YEAR(a.ap_meet_date) As year, s.skill,COUNT(*) as count_comp_conf 
FROM appointment a,skills_data s WHERE a.id_skill=s.id_skill and a.ap_status IN ('complete', 'confirm') 
GROUP BY `id_skill`, `year` 
ORDER BY `YEAR` DESC

我的查询的输出：

 id_skill | year | skill | count_comp_conf 
 -----------------------------------------
 1          2018     A          20        
 2          2018     B          15        
 1          2019     A          10         
 2          2019     B          12 
 3          2019     C          10         

我的预期输出应该是这样的：

 id_skill | year | skill | count_comp_conf | count_cancel | count_missed
 ------------------------------------------------------------------------
 1          2018     A          20             5                 1  
 2          2018     B          15             8                 0  
 1          2019     A          10             4                 1  
 2          2019     B          12             0                 5  
 3          2019     C          10             2                 2

Answer 1

您可以使用conditional aggregation 使用case when expression

SELECT a.id_skill, YEAR(a.ap_meet_date) As year, s.skill,
COUNT(case when a.ap_status IN ('complete', 'confirm') then 1 end) as count_comp_conf,
COUNT(case when a.ap_status = 'cancel' then 1 end) as count_cancel,
COUNT(case when a.ap_status = 'missed' then 1 end) as count_missed
FROM appointment a inner join skills_data s on a.id_skill=s.id_skill 
GROUP BY `id_skill`, `year` 
ORDER BY `YEAR` DESC

Answer 2

SELECT a.id_skill, 
   YEAR(a.ap_meet_date) As year, 
   s.skill,
   SUM(IF(a.ap_status IN ('complete', 'confirm'),1,0)) AS count_comp_conf,
   SUM(IF(a.ap_status='cancel',1,0)) AS count_cancel,
   SUM(IF(a.ap_status='missed',1,0)) AS count_missed
FROM appointment a,skills_data s WHERE a.id_skill=s.id_skill 
GROUP BY `id_skill`, `year` 
ORDER BY `YEAR` DESC;

请尝试将 if 条件与 sum 一起使用。

Answer 3

通过以下查询，您将获得输出。

select id_skill ,
year , 
skill , 
count_comp_conf , 
count_cancel , 
count_missed ( select id_skill, year, skill, if ap_status ='Completed' then count_comp_conf+1, elseif ap_status ='cancelled' then count_cancel +1 else count_missed+1
    from appointment a join skills_data s on (a.id_skill = s.id_skill) group by id_skill, year) group by id_skill,year 
    order by year desc;