制作2列的查询，就好像它们是一个

Question

有包含相同类型的数据的2列：

col_a col_b ... 
Bob Tim .. 
John Frank . 
Bob John 
John Tim 
Bob Bob 
Frank John 

现在我想做的查询是这样的（计算实例：（鲍勃，3 ），（约翰，2），..）：

SELECT col_a, count(*) AS total FROM table1 GROUP BY col_a 

但不是在为col_a运行它，我想在同一时间上为col_a和col_b运行（（鲍勃，4），（约翰，4 ），..）

任何帮助表示赞赏

编辑： 感谢每一个你真棒。

再次感谢根据您Bob Bob列

Answer 1

Select Z.name, Count(*) As Total 
From (
     Select col_a As name 
     From total 
     Union All 
     Select col_b 
     From total 
     ) As Z 
Group By Z.name 

Answer 2

select Name, count(*) as Total 
from (
    select col_a as Name from MyTable 
    union all 
    select col_b from MyTable 
) a 
group by Name 

Answer 3

，我认为你需要组于子：

select idx, sum(count) 
from (
    select col_a as idx, count(*) as count 
    from table 
    union all 
    select col_b as idx, count(*) as count 
    where col_a <> col_b -- avoid dups 
    ) as counts 
group by idx 

或：

select idx, count(*) 
from (
    select col_a as idx 
    from table 
    union all 
    select col_b as idx 
    where col_a <> col_b -- avoid dups 
    ) as counts 
group by idx