AWS Redshift已有按位&、<<、>>操作，如何实现OR和NOT标量操作？

Great question! While AWS Redshift doesn't expose dedicated operators for bitwise OR (|) and bitwise NOT (~) directly, you can easily implement both using the existing bitwise operators and basic arithmetic operations. Here's how:

You can calculate the bitwise OR of two integers using this bitwise arithmetic identity:

a | b = a + b - (a & b)

This works because when you add a and b, any bits set in both numbers get counted twice. Subtracting the bitwise AND (which isolates those overlapping 1s) corrects this, leaving you with the exact result of a bitwise OR.

Example #

To compute 5 | 3 (binary 101 | 011 = 111, which equals 7):

SELECT 5 + 3 - (5 & 3); -- Returns 7

Custom Function (for reusability) #

Wrap this logic into a function to simplify repeated use across queries:

CREATE OR REPLACE FUNCTION bitwise_or(a INT, b INT)
RETURNS INT
AS $$
SELECT a + b - (a & b);
$$ LANGUAGE sql;

-- Usage
SELECT bitwise_or(5, 3); -- Returns 7

Bitwise NOT flips all bits of a number. The implementation varies slightly based on whether you're working with signed or unsigned integers:

For Signed Integers (Redshift's default INT type) #

Use this identity based on two's complement arithmetic:

~x = -x - 1

Example

Flipping bits of 5 (binary 000...0101 → 111...1010, which is -6 in two's complement):

SELECT -5 - 1; -- Returns -6

For Unsigned Integers (e.g., 32-bit values) #

Subtract the number from the maximum value for your target bit width. For 32-bit unsigned integers, that's 2^32 - 1 = 4294967295:

SELECT 4294967295 - 5; -- Returns 4294967290

Custom Functions #

-- Signed bitwise NOT
CREATE OR REPLACE FUNCTION bitwise_not(x INT)
RETURNS INT
AS $$
SELECT -x - 1;
$$ LANGUAGE sql;

-- Unsigned 32-bit bitwise NOT
CREATE OR REPLACE FUNCTION bitwise_not_unsigned_32(x INT)
RETURNS BIGINT
AS $$
SELECT 4294967295 - x;
$$ LANGUAGE sql;

-- Usage
SELECT bitwise_not(5); -- Returns -6
SELECT bitwise_not_unsigned_32(5); -- Returns 4294967290

内容的提问来源于stack exchange，提问作者JairoV