How can I cast an int to a bit in MySQL 5.1?

You cannot!

CAST and CONVERT only work to:

• BINARY[(N)]
• CHAR[(N)]
• DATE
• DATETIME
• DECIMAL[(M[,D])]
• SIGNED [INTEGER]
• TIME
• UNSIGNED [INTEGER]

No room for: BIT, BITINT, TINYINT, MEDIUMINT, BIGINT, SMALLINT, ...

However, you can create your own function cast_to_bit(n):

DELIMITER $$CREATE FUNCTION cast_to_bit (N INT) RETURNS bit(1)BEGIN    RETURN N;END

To try it yourself, you can create view with several conversions like:

CREATE VIEW view_bit AS    SELECT        cast_to_bit(0),        cast_to_bit(1),        cast_to_bit(FALSE),        cast_to_bit(TRUE),        cast_to_bit(b'0'),        cast_to_bit(b'1'),        cast_to_bit(2=3),        cast_to_bit(2=2)

... and then describe it!

DESCRIBE view_bit;

Ta-dah!! Everyone is bit(1) now!!!

Try using case:

CREATE TABLE myNewTable ASSELECT (case myIntThatIsZeroOrOne when 1 then true else false end) AS myBitFROM myOldtable

Try CONV(N,from_base,to_base)

Converts numbers between different number bases. Returns a string representation of the number N, converted from base from_base to base to_base. Returns NULL if any argument is NULL. The argument N is interpreted as an integer, but may be specified as an integer or a string. The minimum base is 2 and the maximum base is 36. If to_base is a negative number, N is regarded as a signed number. Otherwise, N is treated as unsigned. CONV() works with 64-bit precision.

for example.

select CONV(9, 10, 2);