MySQL always returning BIT values as blank

Question

From my create table script, I\'ve defined the hasMultipleColors field as a BIT:

hasMultipleColors BIT NOT NULL,

When running an INSERT, th

Answer 1

You can cast BIT field to unsigned.

  SELECT CAST(hasMultipleColors AS UNSIGNED) AS hasMultipleColors 
  FROM pumps 
  WHERE id = 1

It will return 1 or 0 based on the value of hasMultipleColors.

Answer 2

The actual reason for the effect you see, is that it's done right and as expected.

The bit field has bits and thus return bits, and trying to output a single bit as a character will show the character with the given bit-value – in this case a zero-width control character.

Some software may handle this automagically, but for command line MySQL you'll have to cast it as int in some way (e.g. by adding zero).

In languages like PHP the ordinal value of the character will give you the right value, using the ord() function (though to be really proper, it would have to be converted from decimal to binary string, to work for bit fields longer than one character).

EDIT:
Found a quite old source saying that it changed, so a MySQL upgrade might make everything work more as expected: http://gphemsley.wordpress.com/2010/02/08/php-mysql-and-the-bit-field-type/

Answer 3

You need to cast the bit field to an integer.

mysql> select hasMultipleColors+0 from pumps where id = 1;

This is because of a bug, see: http://bugs.mysql.com/bug.php?id=43670. The status says: Won't fix.

Answer 4

You need to perform a conversion as bit 1 is not printable.

SELECT hasMultipleColors+0 from pumps where id = 1;

See more here: http://dev.mysql.com/doc/refman/5.0/en/bit-field-literals.html