How to deal with this join situation?

Hello,

My agency has a request in a project with Treasury (IPP) and here is the situation in which we have tried a few days but getting no where:

• Two tables:  Table1 (col1, col2), Table2 (col1, col3)
• Table2 has rows only when a condition is met for Table1.  So Table1 may have 10 rows and Table2 only 2.  For those two rows, co1 is the same as Table1.col1 but col3 could be the same as Table1.col2, or different
• we need to query all distinct rows from both tables (we try left outer join here)
• for Table2.col3, if the value is dfferent from table1.col2, we need to have this value