BIN(N): Returns a string representation of the binary value of N, where N is a long (BIGINT) number : BIN « String Functions « MySQL Tutorial

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2. String Functions
3. BIN

Returns NULL if N is NULL.

mysql>
mysql> SELECT BIN(12);
+---------+
| BIN(12) |
+---------+
| 1100    |
+---------+
1 row in set (0.00 sec)

mysql>
mysql> SELECT BIN(NULL);
+-----------+
| BIN(NULL) |
+-----------+
| NULL      |
+-----------+
1 row in set (0.00 sec)