即使没有记录，也请选择日期范围内的所有记录

Question

我有一个员工及其出勤的数据库。我必须创建出勤日期范围报告。

出勤数据库表

我正在使用以下查询

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，但是数据库中没有一些日期记录，我希望那些日期显示空值对应于那些日期，如下图所示。

Answer 1

试试这个。我无法运行它，但想法是根据此answer生成日期范围。

1. 将此日期范围用作派生表d。

2. 执行d left join attendance添加您的条件，这样您就会获得匹配数据的所有列，而null则不匹配数据。

3. 除了员工ID之外，这将为您提供其余数据。我建议你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