PostgreSQL: insert from another table

Question

I\'m trying to insert data to a table from another table and the tables have only one column in common. The problem is, that the TABLE1 has columns that won\'t accept null value

Answer 1

Just supply literal values in the SELECT:

INSERT INTO TABLE1 (id, col_1, col_2, col_3)
SELECT id, 'data1', 'data2', 'data3'
FROM TABLE2
WHERE col_a = 'something';

A select list can contain any value expression:

But the expressions in the select list do not have to reference any columns in the table expression of the FROM clause; they can be constant arithmetic expressions, for instance.

And a string literal is certainly a value expression.