Question

I have a SQL data like this:

id  date_start  date_end  identical_value
1   1           1         a
2   1           3         b
3   2           3         c

I need return multiple semi-identical results, but only with ID and a new column. Below an example:

id  date_reference  identical_value
1   1               a
2   1               b
2   2               b
2   3               b
3   2               c
3   3               c

Note that the column date_reference starts on date_start and end on date_end.

I have a good notion on basic SQL, but I don’t undestand to much of loopings, and I think that maybe is essential here.

What I need: a good example — not exactly the answer — to I understand if it is possible or not, or what I need to search (functions, keyworkds…) of MySQL to do.

Answer 1

Create a table with integers from 1 to some very large numbers. Then you can join on the number table to expand the date range:

select  yt.id
,       num.Number as date_reference
,       yt.identical_value
from    YourTable yt
join    NumberTable num
on      num.Number between yt.date_start and yt.date_end