-- In this case since the significant bits 
-- are 0 and 1, the AND operation is 
-- between 0 and 1. 
-- BITAND(1,1) = 1 and other three
-- combination (0,0), (0,1) and (1,0)
-- result in 0
-- Refer Logic Gates (AND truth table)

SELECT
 BITAND(0,0) bitand_00,
 BITAND(0,1) bitand_01,
 BITAND(1,0) bitand_10,
 BITAND(1,1) bitand_11
FROM DUAL;

-- For other input values, they get
-- converted to binary values and 
-- the rightmost bit values are
-- used in the AND operation.

SELECT  q_tab.x,
 BITAND(q_tab.x,q_tab.x)   "BITAND(X,X)",
 BITAND(q_tab.x,q_tab.x-1) "BITAND(X,X-1)",
 BITAND(q_tab.x,0)         "BITAND(X,0)",
 BITAND(q_tab.x,1)         "BITAND(X,1)"
FROM
 (SELECT  level x
  FROM DUAL
  CONNECT BY level <=10
 ) q_tab;

-- Refer BITAND(X, X) Analysis
-- Refer BITAND(X, X-1) Analysis
-- Refer BITAND(X, 1) Analysis

-- Any value of X with 0 in 
-- BITAND(X, 0) results in 0 
-- as shown in the output of
-- above query.