postgresql - compare two tables grouped by a column

Question

i don't know if my title for this question is correct, but here is my question

I have two tables (TB1 and TB2) both have same columns, here is the structure..

TABLE_NAME  |  COLUMN_NAME  |  DATA_TYPE

then I want to compare all the values in column_name grouped by table_name and data_type

the returning table should at least look like this (with sample data)...

TABLE_NAME   |  COLUMN_NAME (TB1)  |  COLUMN_NAME (TB2)  |  DATA_TYPE
user_account |       id            |        id           |  charvar
user_account |      user_name      |     user_name       |   charvar
user_account |      date_expire    |         -           |   charvar    
user_account |        -            |         gender      |   int
user_account |     gender          |         -           |   charvar
employee     |       id            |        id           |  charvar
employee     |       full_name     |        full_name    |  charvar

sorry but I have not started any query, cause I really don't know where / what to start.. thanks in advance to all who will response :D

Answer 1

I think you want a full outer join :

select coalesce(tb1.table_name, tb2.table_name) as table_name,
       tb1.column_name, tb2.column_name,
       coalesce(tb1.data_type, tb2.data_type) as data_type
from tb1 full outer join
     tb2
     on tb1.table_name = tb2.table_name and
        tb1.column_name = tb2.column_name and
        tb1.data_type = tb2.data_type;