Postgresql SQL: How check boolean field with null and True,False Value?

There are 3 states for boolean in PG: true, false and unknown (null). Explained here: Postgres boolean datatype

Therefore you need only query for NOT TRUE:

SELECT * from table_name WHERE boolean_column IS NOT TRUE;

On PostgreSQL you can use:

SELECT * FROM table_name WHERE (boolean_column IS NULL OR NOT boolean_column)

I'm not expert enough in the inner workings of Postgres to know why your query with the double condition in the WHERE clause be not working. But one way to get around this would be to use a UNION of the two queries which you know do work:

SELECT * FROM table_name WHERE boolean_column IS NULL
UNION
SELECT * FROM table_name WHERE boolean_column = FALSE

You could also try using COALESCE:

SELECT * FROM table_name WHERE COALESCE(boolean_column, FALSE) = FALSE

This second query will replace all NULL values with FALSE and then compare against FALSE in the WHERE condition.

1. select *from table_name where boolean_column is False or Null;

   Is interpreted as "( boolean_column is False ) or (null)".

   It returns only rows where boolean_column is False as the second condition is always false.

2. select *from table_name where boolean_column is Null or False;

   Same reason. Interpreted as "(boolean_column is Null) or (False)"

3. select *from table_name where boolean_column is Null or boolean_column = False;

   This one is valid and returns 2 rows: false and null.

I just created the table to confirm. You might have typoed somewhere.