Add empty rows to select

Question

Hi I have the following select
select bz.type_id, bz.year, bz.amount_cars
      from  my_table bz
        order by bz.type_id, bz.yearthe output looks like this:
type_id, year, amount_cars
581     2013     3
581     2014     3
581     2015     3
581     2016     3
581     2017     3
641     2013     59
641     2014     60My problem: I need to always show the next five years. If the table doesn't have it for the type_id then it should be generated some how:
type_id, year, amount_cars
581     2013     3
581     2014     3
581     2015     3
581     2016     3
581     2017     3
641     2013     59
641     2014     60
641     2015     0
641     2016     0
641     2017     0Hope you can help.
Cheers
Tobias

Answer 1

Hi Tobias,
you need a cartesian join (or cross join) between types and years.
I have assumed that years are starting from next year (from sysdate).
Here my test:
WITH mytable AS
   SELECT 581 type_id, 2013 yr, 3  amount_cars FROM DUAL UNION ALL
   SELECT 581 type_id, 2014 yr, 3  amount_cars FROM DUAL UNION ALL
   SELECT 581 type_id, 2015 yr, 3  amount_cars FROM DUAL UNION ALL
   SELECT 581 type_id, 2016 yr, 3  amount_cars FROM DUAL UNION ALL
   SELECT 581 type_id, 2017 yr, 3  amount_cars FROM DUAL UNION ALL
   SELECT 641 type_id, 2013 yr, 59 amount_cars FROM DUAL UNION ALL
   SELECT 641 type_id, 2014 yr, 60 amount_cars FROM DUAL
), got_years AS
   SELECT EXTRACT(YEAR FROM SYSDATE) + LEVEL yr
     FROM DUAL
  CONNECT BY LEVEL <=5
SELECT a.yr, b.type_id, NVL(c.amount_cars, 0) amt_cars
  FROM got_years a
       CROSS JOIN (SELECT distinct type_id from mytable) b
       LEFT OUTER JOIN mytable c ON (a.yr = c.yr AND b.type_id = c.type_id)
ORDER BY b.type_id, a.yr;
Output:
        YR    TYPE_ID   AMT_CARS
      2013        581          3
      2014        581          3
      2015        581          3
      2016        581          3
      2017        581          3
      2013        641         59
      2014        641         60
      2015        641          0
      2016        641          0
      2017        641          0Instead of cross joining with (SELECT distinct type_id from mytable) you might want to cross join with a table having list of type_id.
Regards.
Al