如何在兩個語句上使用連接？

Question

我有一個說法，記錄有多少條記錄attr3 = 1。

SELECT 'Dept' AS table_name, COUNT(*) 
FROM ((select attr3 from table1) union all 
     (select attr3 from table2) 
    ) t 
WHERE attr3 = '1'; 

現在我需要有一個做同樣的事情，但數多少記錄有attr3 = 2另一個語句。

SELECT 'Dept' AS table_name, COUNT(*) 
    FROM ((select attr3 from table1) union all 
      (select attr3 from table2) 
     ) t2 
    WHERE attr3 = '2'; 

理想情況下，數據將在此格式

Dept   count(*) 
attr3 = 1   4 
attr3 = 2   6 

，如果我單獨做報表，此方法效果顯示，我只是單純的想加入他們在一起。誰能幫忙？

Answer 1

簡單的GROUP BY和WHERE attr3 in()應該就足夠了。

SELECT Z.attr3 as Dept, count(*) as cnt 
FROM (SELECT attr3 FROM table1 
     UNION ALL 
     SELECT attr3 FROM table2) Z 
WHERE attr3 in ('1','2') 
GROUP BY Z.attr3 

由於attr3通過where子句定義要通過它通過計算，只需組和聯合後的結果限制爲您的1,2組。

Answer 2

該團隊將完成這項工作。

SELECT 'Dept' AS table_name, COUNT(*) 
FROM ((select attr3 from table1) union all 
     (select attr3 from table2) 
    ) t2 
WHERE attr3 = '2' 
group by dept; 

http://www.w3schools.com/sql/sql_groupby.asp