MySQL 5.6

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select version();


version()


5.6.51


create table Companies( 
                        id   int, 
                        name varchar(25) 
                      )
insert into Companies values(0,'Test1'),(1,'Test2')

Records: 2  Duplicates: 0  Warnings: 0


create table Holidays( 
                       id int not null, 
                       company_id int, 
                       name varchar(25),
                       primary key(id)
                       )
insert into Holidays(id,company_id,name)
select @rn := @rn + 1, c1.id, concat('Holiday',(c1.id+1))
  from Companies c1
  join Companies c2
 join (select @rn := -1) as q_iter

Records: 4  Duplicates: 0  Warnings: 0


select * from Holidays


id
company_id
name


0
0
Holiday1

1
1
Holiday2

2
0
Holiday1

3
1
Holiday2