Using DATE_ADD with a Column Name as the Interval Value

Question

I have a table which contains products, a start date and an interval value :

product_name                    start_date              expiry_period
Domain Reg         


        

Answer 1

You need to test for each one individually:

select product_name, start_date, expiry_period,
       (case when expiry_period like '%day'
             then DATE_ADD(start_date, INTERVAL expiry_period + 0 DAY) as end_date
             when expiry_period like '%week'
             then DATE_ADD(start_date, INTERVAL expiry_period + 0 WEEK) as end_date
             when expiry_period like '%month'
             then DATE_ADD(start_date, INTERVAL expiry_period + 0 MONTH) as end_date
             when expiry_period like '%year'
             then DATE_ADD(start_date, INTERVAL expiry_period + 0 YEAR) as end_date
       end)
from tbl_products;

The arithmetic (+ 0 and * 7) converts the string to a number.