gistfile1.sql

select * from tims;
 a | b 
---+---
 t | t
 t | f
 t | 
   | 
 f | f
(5 rows)

select * from tims where a is true and b is false;
 a | b 
---+---
 t | f
(1 row)

select * from tims where a and not b;
 a | b 
---+---
 t | f
(1 row)