製作2列的查詢，就好像它們是一個

Question

有包含相同類型的數據的2列：

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

現在我想做的查詢是這樣的（計算實例：（鮑勃，3 ），（約翰，2），..）：

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

但不是在爲col_a運行它，我想在同一時間上爲col_a和col_b運行（（鮑勃，4），（約翰，4 ），..）

任何幫助表示讚賞

編輯： 感謝每一個你真棒。

再次感謝根據您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

，我認爲你需要組於子：

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