需要帮助来计算单列

Question

我需要从两个表中获取单个列的计数。

代码sn-p

select 
    ((select count(Gender) from tableA) +
     (select Count(Gender) from tableB)) as Total Count

select 
    ((select Sum(Case when Gender = M then 1 else 0) from tableA) +    
     (select Sum(Case when Gender = M then 1 else 0) from tableB)) as Male Count

select 
    ((select Sum(Case when Gender = F then 1 else 0) from tableA) +    
     (select Sum(Case when Gender = F then 1 else 0) from tableB)) as Female Count

1. 使用这些代码 sn-ps，我可以得到 3 个行集的结果。有没有办法在一个包含三列的行集中获得所有三个计数（总计数、男性计数、女性计数）？

2. 其他情况，我需要根据不同的 if else 条件来获取同一存储过程中相同列的计数。有没有办法获得这些计数，而不是为每个条件重复相同的代码？

Answer 1

看来你可以尝试联合这两个表并应用聚合。

SELECT COUNT(GENDER),SUM(CASE WHEN X.GENDER='MALE' THEN 1 ELSE 0 END)AS MALE_COUNT,
  SUM(CASE WHEN X.GENDER='FEMALE' THEN 1 ELSE 0 END)AS FEMALE_COUNT
 FROM
(
  select gender from tablea
  union all
  select gender from tableb  
)AS X