How to show the record in sql with only the last 30 days

Question

the original data in table X

+----------+-----+
|Date      |Count|
+----------+-----+
|2014-01-15|44   |
+----------+-----+
|2014-01-01|5    |
+----------+-----+
|2013-12-10|1    |
+----------+-----+

what I want to display is below :

+----------+-----+
|Date      |Count|
+----------+-----+
|2014-01-15|44   |
+----------+-----+
|2014-01-14|0    |
+----------+-----+
|2014-01-13|0    |
+----------+-----+
|2014-01-12|0    |
+----------+-----+
|...       |...  |

*p/s and so on until 2013-12-14 or 2013-12-15

*how to solve the problem - 'curdate'/'NOW'/'subdate' is not a recognized built-in function name.

Answer 1

In MySQL, you have to do some thing like this:

select date_sub(date(now()), interval n.n day), coalesce(t.`count`, 0)
from (select 0 as n union all select 1 union all select 2 union all select 3 union all
      . . .
      select 30
     ) n left join
     table t
     on t.date = date_sub(date(now()), interval n.n day);

The first part is a manual list of 30 numbers.

Answer 2

One option is to create a date lookup table and then use an outer join with date_sub . This query should work for you:

select d.datefield, coalesce(x.count,0) count
from datelookup d
  left join x on d.datefield = x.datefield
where d.datefield > date_sub(curdate(), interval 30 day)
  and d.datefield <= curdate()
order by d.datefield desc

• SQL Fiddle Demo