Unable to Join Same Table (POSTGRES)

[saklanipankaj]

SELECT  SUM(table1.a +table2.a)
    FROM  t1 table1
    JOIN t1 table2 ON table1.a = table2.a;

ERROR: 42712: table name "t1" specified more than once

Unable to join the same table

[cheziyi]

We will need to investigate this further.