SQL SELECT COUNT（*）

Question

我有兩個表具有這種結構：

TABLE_1：

Column_A(P_Key) Column_B 
    Val1    Location1 
    Val2    Location1 
    Val3    Location2 
    Val4    Location3 
    Val4    Location4 
    Val4    Location5 

TABLE_2：

Column_A(P_Key) Column_B Column_C 
    Location1   Person_1 Person_2 
    Location2   Person_1 Person_3 
    Location3   Person_3 Person_4 
    Location4   Person_1 Person_5 
    Location5   Person_2 Person_3 

我需要一個查詢來計數的項目數量每個人都負責在每個位置：

例如，查詢應返回：

Person  Total 
Person_1  4 
Person_2  3 
Person_3  3 
Person_4  1 
Person_5  1 

這是SQL Server 2008 R2

謝謝！

Answer 1

我會傾向於unpivot的第二個表，然後再彙總：

select person, count(*) 
from ((select column_b as person 
     from table2 t2 join 
      table1 t1 
      on t2.column_a = t1.column_b 
    ) union all 
     (select column_c as person 
     from table2 t2 join 
      table1 t1 
      on t2.column_a = t1.column_b 
    ) 
    ) p 
group by person 
order by count(*) desc; 

Answer 2

如果我正確unterstand您的需要此查詢應符合您的期望：

SELECT DISTINCT t.column_a AS person, 
    (SELECT COUNT(*) FROM table_2 t1 WHERE t1.column_b = t.column_a) + (SELECT COUNT(*) FROM table_2 t2 WHERE t2.column_c = t.column_a) AS Total 
FROM 
    table_2 t