How to join parent and child tables to get the following using SQL or HQL

Question

Given Table1 and Table2 as below how to return the resultset shown below?

TABLE1

TBL1_PK     TBL1_COL2
1            A  

TABLE2

TBL2_PK  TABLE1_FK    ROLE_CD           FIRST_NAME  LAST_NAME
1      1           ROLE_1       DEF   GHI
2      1           ROLE_2       JKL   MNP
3      1           ROLE_3       RST   UVW

RESULSET

TBL1_COL2  ROLE_1_FIRST_NAME ROLE1_LAST_NAME ROLE_2_FIRST_NAME ROLE_2_LAST_NAME
A          DEF               GHI             JKL               MNP

Answer 1

You can use aggregation to do this:

select t1.TBL1_COL2,
    max(case 
            when t2.role_cd = 'ROLE_1'
                then t2.first_name
            end) ROLE_1_FIRST_NAME,
    max(case 
            when t2.role_cd = 'ROLE_1'
                then t2.last_name
            end) ROLE1_LAST_NAME,
    max(case 
            when t2.role_cd = 'ROLE_2'
                then t2.first_name
            end) ROLE_2_FIRST_NAME,
    max(case 
            when t2.role_cd = 'ROLE_2'
                then t2.last_name
            end) ROLE2_LAST_NAME
from table1 t1
join table2 t2 on t1.tbl1_pk = t2.table1_fk
group by t1.TBL1_COL2

Answer 2

Join table 1 to table 2 twice with 2 different aliases. Then restrict the aliases as needed to get role_1 from one and role_2 from the other

select
 T1.TBL1_COL2 as "TBL1_COL2",
 T2R1.FIRST_NAME as "Role_1_first_name",
 T2R1.Last_name as "Role_1_last_name",
 T2R2.First_name as "Role_2_first_name",
 T2R2.Last_name as "Role_2_last_name"
from 
   Table1 as T1
 inner join Table2 as T2R1 on T1.TBL1_PK = T2R1.Table1_fk
 inner join Table2 as T2R2 on T2.TBL1_PK = T2T2.Table1_fk
where
    T2R1.role_cd = "Role_1"
and T2T2.role_cd = "Role_2";