I have created 3 tables which contain Parent, Child, Mark and I want to combine three tables together using union query

In Parent table:

Id int (primary key),
Firstname varchar(50),
Email varchar(50)

In Child table:

Mid int (primary key),
Mark1 int,
Mark2 int,
Id(foreign key)

In Mark table:

Uid (primary key),
Mark3 int,
Id int (foreign key)

I want results to be like using Union query:

Id Firstname Mark1 Mark2 Mark3
-- --------- ----- ----- -----
1   john      80    70    60