Question

我有2张桌子。表1和表2.

表1数据：

 Id   org_id  start_date    end_date     month
'1', '46', '2015-01-01', '2015-01-31', 'January'
'2', '46', '2015-02-01', '2015-02-28', 'February'
'3', '46', '2015-03-01', '2015-03-31', 'March'
'4', '46', '2015-04-01', '2015-04-30', 'April'
'5', '46', '2015-05-01', '2015-05-31', 'May'
'6', '46', '2015-06-01', '2015-06-30', 'June'
'7', '46', '2015-07-01', '2015-07-31', 'July'
'8', '46', '2015-08-01', '2015-08-31', 'August'
'9', '46', '2015-09-01', '2015-09-30', 'September'
'10', '46', '2015-10-01', '2015-10-31', 'October'
'11', '46', '2015-11-01', '2015-11-30', 'November'
'12', '46', '2015-12-01', '2015-12-31', 'December'

表2数据：

Id   org_id   from_date  emp_id
'48', '46', '2015-06-09'   1
'49', '46', '2015-06-09'   1
'50', '46', '2015-06-01'   2
'51', '46', '2015-05-20'   1
'56', '46', '2015-07-07'   2

这是我的疑问：

select t1.month,count(t2.emp_id) as count
from Table1 t1
left outer join  Table2 t2 on t2.from_date between t1.start_date and t1.end_date
where t2.org_id=46 group by t1.month

我得到的输出是：

month   count
'July', '1'
'June', '3'
'May', '1'

我期待的输出是：

 month    count
'January', '0'
'February', '0'
'March', '0'
'April', '0'
'May', '1'
'June', '3'
'July', '1'
'August', '0'
'September', '0'
'October', '0'
'November', '0'
'December', '0'

我使用左外连接。但左表中的所有记录都没有获取。

任何帮助!!

Answer 1

您必须将where身份的部分放入on clase：

select t1.month,count(t2.emp_id) as count
from Table1 t1
left outer join  Table2 t2 on t2.from_date between t1.start_date and t1.end_date
and t2.org_id=46 group by t1.month

如果您不这样做，则会有inner join

Answer 2

试试这个..

SELECT t1.month,COUNT(t2.emp_id) AS COUNT
    FROM Table1 t1
    LEFT JOIN  Table2 t2 ON t2.from_date BETWEEN t1.start_date AND t1.end_date
    AND t2.org_id=46 GROUP BY t1.month

加入两个表是行不通的

2 个答案: