0

Using PostgreSQL if I cast

65::bit(8)::"char"

I get 0, if I however cast

65::bit(8)::int::"char"

I get A as I would expect.

SELECT
  v,
  v::bit(8)::"char" AS noint,
  v::bit(8)::int::"char" AS "viaInt"
FROM (VALUES (65)) AS t(v);
 v  | noint | viaInt 
----+-------+--------
 65 | 0     | A
(1 row)
0

That's because the cast directly to "char" without going through int first is taking the first character from the stringification of the bitfield.

SELECT 65::bit(8);
   bit    
----------
 01000001
(1 row)

SELECT '01000001'::"char", '0'::"char";
 char | char 
------+------
 0    | 0
(1 row)

If that was greater than 128, you'd have a one in that position,

SELECT 128::bit(8);
   bit    
----------
 10000000
(1 row)

Casting that to "char" would give you a 1 rather than a 0,

SELECT 128::bit(8)::"char";
 char 
------
 1
(1 row)

Keep in mind, "char" is signed, so the range is [-128,127]. For this reason you can't actually go from bit(8) to "char" without first shifting those bits. For example

SELECT 128::bit(8)::int::"char";
ERROR:  "char" out of range

See also

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.