Question

Hi i am currently studying sql and I have 2 one to many tables but I do not understand how to combine them to a many to many. I have a joining table.

table parent
columns parent and parent id

table child
columns child and childid

table parentchild –(Join table selecting parents with childid)
columns parentid and childid

Here is my codes.

select parent.name, parentchild.childid from parent
join parentchild
on parent.parentID = parentchild.parentid

select child.name, parentchild.parentid from child
join parentchild 
on child.childID = parentchild.childid

Answer 1

The solution is to write a single query which joins the parent table to the parentchild table and then join the parentchild table to the child table.

select p.name, c.name 
from parent p
join parentchild pc
    on p.parentid = pc.parentid  -- joins parent to parentchild
join child c
    on c.childID = pc.childid  -- joins parentchild to child