Is it good/bad design to join composite key with underscore in url?

I'm looking for the best practices on RESTful API design for the following use case:

Table1     Table2
Id1        Id1
Id2        Id2
Id3        Id3
Name       Name
           Table1Id1(FK to Table1)
           Table1Id1(FK to Table1)
           Table1Id1(FK to Table1)

Suppose i have endpoints like below for Table1:

/root/table1 (to get list of records)
/root/table2 (to get single record by primary key)

Now here my question is which would be the best way from below two to represent composite key in second url :

/root/e1/Id1/Id2/Id3

or 

/root/e1?Id1=1&Id2=2&Id3=3

Suppose i have endpoints like below for Table2:

/root/table1/Table1Id1_Table1Id2_Table1Id1/table2 (to get list of records for table2 by table1).

Now here is my question that is above url valid and appropriate in case of composite key?

Any advice on a good pattern to follow for this use case would be greatly appreciated.