选择日期范围内的所有记录，即使没有记录存在

Question

我有一个员工数据库及其出勤率。我必须创建出勤日期范围报告。

考勤数据库表

我正在使用下面的查询

SELECT a.* FROM attendance a WHERE a.user_id=10 AND (a.date BETWEEN '2017-01-06' AND '2017-01-10')

结果：-

我还想要所有给定日期范围的记录，但数据库中不存在某些日期记录，我希望日期显示空值以对应于该日期，如下图所示。

Answer 1

试试这个。我无法运行它，但我的想法是根据此answer 生成日期范围。

1. 将此日期范围用作派生表d。

2. 做一个dleft joinattendance添加你的条件，这样你就会得到所有匹配数据的列和null不匹配的数据。

3. 这将为您提供除员工 ID 之外的其余数据。我建议您可以在选择查询中对其进行硬编码。

   select * from 
       (select a.Date 
           from 
           (
               select curdate() - INTERVAL (a.a + (10 * b.a) + (100 * c.a)) DAY as Date
               from (select 0 as a union all select 1 union all select 2 union all select 3 union all select 4 union all select 5 union all select 6 union all select 7 union all select 8 union all select 9) as a
               cross join (select 0 as a union all select 1 union all select 2 union all select 3 union all select 4 union all select 5 union all select 6 union all select 7 union all select 8 union all select 9) as b
               cross join (select 0 as a union all select 1 union all select 2 union all select 3 union all select 4 union all select 5 union all select 6 union all select 7 union all select 8 union all select 9) as c
           ) a
           where a.Date between '2017-01-06' AND '2017-01-10' 
       ) d
   left join 
       attendance a
   on d.date = a.date
   where 
   a.user_id=10