Question

我有一个声明计算有attr3 = 1的记录数。

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

现在我需要另一个声明做同样事情的声明，但要计算有attr3 = 2的记录数。

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

理想情况下，数据将以此格式显示

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

如果我单独执行语句，此方法有效，我只是想将它们连接在一起。有人可以帮忙吗？

Answer 1

简单的GROUP BY和WHERE attr3 in()就足够了。

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

由于attr3定义了您想要计数的组，因此只需将其分组并通过where子句将结果限制为1,2之后的结果。

Answer 2

小组将完成这项工作。

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

如何在两个语句中使用连接？

2 个答案: