开发指南—函数—位函数

mysql> SELECT BIT_COUNT(29), BIT_COUNT(b'101010');
+--------------+----------------------+
| BIT_COUNT(29) | BIT_COUNT(b'101010') |
+--------------+----------------------+
|            4 |                    3 |
+--------------+----------------------+
1 row in set (0.00 sec)
mysql> SELECT BIT_COUNT(NULL);
+-----------------+
| BIT_COUNT(NULL) |
+-----------------+
|            NULL |
+-----------------+
1 row in set (0.00 sec)
mysql> SELECT 3 & 2;
+-------+
| 3 & 2 |
+-------+
|     2 |
+-------+
1 row in set (0.01 sec)