insert into table B from table A with condition

Question

I have a table A with below columns

Name age phoneNumber
A     26 12345
B     34 87654
C     5  98765

my output table also contains same column names with no data

I need to generate output table like below mentioned

Name age phoneNumber
A     10 12345
A     10 12345
A     6 12345
B     10 87654
B     10 87654
B     10 87654
B     4 87654
C     5  98765

that is everytime I will substract age with 10 until age < 10 if in input table, if the age is less that 10 then move that row as it is to output table

Can anyone please guide me how to do this operation to get desired output

Answer 1

This looks like a good spot to use a recursive cte:

with cte as (
    select name, age, age % 10 new_age, phoneNumber, 1 i from mytable
    union all
    select name, age, 10, phoneNumber, i + 1
    from cte
    where age > i * 10
)
select name, new_age age, phoneNumber from cte order by name, age desc

Demo on DB Fiddle :

name | age | phoneNumber
:--- | --: | ----------:
A    |  10 |       12345
A    |  10 |       12345
A    |   6 |       12345
B    |  10 |       87654
B    |  10 |       87654
B    |  10 |       87654
B    |   4 |       87654
C    |   5 |       98765