MySQL in a Nutshell, 2nd Edition

Name

MAKE_SET()

Synopsis

MAKE_SET(bits, string1, string2, ...)

This function converts the decimal number in bits to binary and returns a comma-separated list of values for all the bits that are set in that number, using string1 for the low-order bit, string2 for the next lowest bit, etc. Here is an example:

SELECT BIN(9) AS 'Binary 9',
MAKE_SET(100, 'A','B','C','D')
AS Set;

+----------+------+
| Binary 9 | Set  |
+----------+------+
| 1001     | A,D  |
+----------+------+

The binary equivalent of 9 is 1001. The first bit starting from the right of the binary number shown is 1 (or on), so the first string in the list is put into the results. The second and third bits of the binary number are 0, so the second and third strings ('B' and 'C') are left out of the results. The fourth bit counting from the right is 1, so the fourth string of the list is added to the results.