Convert a string or a number to a string in hexadecimal format with the HEX() function : hexadecimal « Data Types « MySQL Tutorial

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2. Data Types
3. hexadecimal

mysql>
mysql> SELECT HEX('cat');
+------------+
| HEX('cat') |
+------------+
| 636174     |
+------------+
1 row in set (0.02 sec)

mysql>
mysql> SELECT 0x636174;
+----------+
| 0x636174 |
+----------+
| cat      |
+----------+
1 row in set (0.00 sec)

mysql>