Can I concatenate two sql column and use it in DATE

I have been stuck with this issue for hours now.

I have a table called subscribe with the following fields

id (int)
sub_type (week, month, year) (Varchar)
sub_duration (int)
last_renewal (Date)

I want to merge the sub_duration and sub_type and add it to the last_renewal (to get the expiring date), Then check if the result is greater/lesser than the current date. Below is what I have done.

SELECT s.*
FROM subscription s
WHERE (SELECT DATE_ADD(s.last_renewal, INTERVAL (CONCAT(s.sub_duration), ' ', s.sub_type)))< CURDATE()

CodePudding user response：

You can combine CASE with DATE_SUB to get the expiration date in a subquery. Then it's easy to compare and analyze each case.

For example:

select *,
  case when expiring_date < curdate() then 'Expired'
       when expiring_date > curdate() then 'Active'
       else 'Expires Today'
  end as status
from (
  select *,
    case when sub_type = 'week' then date_add(last_renewal, interval sub_duration week)
         when sub_type = 'month' then date_add(last_renewal, interval sub_duration month)
         when sub_type = 'year' then date_add(last_renewal, interval sub_duration year)
    end as expiring_date
  from subscription
) x

Result:

 id  sub_type  sub_duration  last_renewal  expiring_date  status  
 --- --------- ------------- ------------- -------------- ------- 
 1   month     2             2021-04-12    2021-06-12     Expired 
 2   week      1             2021-07-11    2021-07-18     Expired 
 3   week      4             2021-11-11    2021-12-09     Active

See running example at DB Fiddle.

CodePudding user response：

INTERVAL accepts keywords, not strings

you can use case when

The key part of sql is like this

select *
  from (
select 'week' sub_type, 1 sub_duration union all
select 'year' sub_type, 1 sub_duration) s
 where case when s.sub_type = 'week'
            then DATE_ADD(now(), INTERVAL s.sub_duration week) 
            when s.sub_type = 'month'
            then DATE_ADD(now(), INTERVAL s.sub_duration month) 
            when s.sub_type = 'year'
            then DATE_ADD(now(), INTERVAL s.sub_duration year) 
       end > now()