在mysql查询上添加零值缺失行

Question

问题是这样的，我有一个查询，该查询返回一个日期和该特定日期的计数，但是我想要的是出现在该范围内（因为该表中不存在）的日期出现但带有零值。

我的查询是这样的：

     SELECT fechacierre, COUNT(idcliente) as cantidad
     FROM cliente
     WHERE fechacierre BETWEEN DATE_ADD('2017-02-21', INTERVAL -6 DAY) AND '2017-02-21'
     GROUP BY fechacierre

给出以下结果：

------------------------
fechacierre | cantidad
------------------------
2017-02-15  | 3
------------------------
2017-02-17  | 1
------------------------
2017-02-20  | 3
------------------------
2017-02-21  | 2
------------------------

如何获取值为0的（2017-02-16），（2017-02-18）和（2017-02-19）的值？

提前致谢！

Answer 1

您可以使用以下所有日期生成一个辅助表：

select @rowNum := @rowNum +1, DATE_ADD('2017-02-21', INTERVAL -@rownum DAY) as fechacierre from Any_table_with_some_records, (select @rowNum := 0) t

那你就可以加入

SELECT fechacierre, COUNT(idcliente) as cantidad
FROM cliente
RIGHT JOIN aux ON aux.fechacierre = cliente.fechacierre
WHERE fechacierre BETWEEN DATE_ADD('2017-02-21', INTERVAL -6 DAY) AND '2017-02-21'
     GROUP BY fechacierre

这是一个主意，我没有测试。

Answer 2

您可以使用具有以下所有时间的表进行右联接来解决它：

SELECT fechacierre, COUNT(idcliente) as cantidad
     FROM cliente RIGHT JOIN (select * from 
(select adddate('1970-01-01',t4.i*10000 + t3.i*1000 + t2.i*100 + t1.i*10 + t0.i) selected_date from
 (select 0 i union select 1 union select 2 union select 3 union select 4 union select 5 union select 6 union select 7 union select 8 union select 9) t0,
 (select 0 i union select 1 union select 2 union select 3 union select 4 union select 5 union select 6 union select 7 union select 8 union select 9) t1,
 (select 0 i union select 1 union select 2 union select 3 union select 4 union select 5 union select 6 union select 7 union select 8 union select 9) t2,
 (select 0 i union select 1 union select 2 union select 3 union select 4 union select 5 union select 6 union select 7 union select 8 union select 9) t3,
 (select 0 i union select 1 union select 2 union select 3 union select 4 union select 5 union select 6 union select 7 union select 8 union select 9) t4) v
where selected_date between DATE_ADD('2017-02-21', INTERVAL -6 DAY) and '2017-02-21') t ON fechacierre = selected_date
     WHERE fechacierre BETWEEN DATE_ADD('2017-02-21', INTERVAL -6 DAY) AND '2017-02-21'
     GROUP BY fechacierre