when the from_str is "", use REPLACE FUNC.
+-----------------------------------------------------------------------+
| REPLACE('www.mysql.com', '', 'tidb') |
+-----------------------------------------------------------------------+
| tidbwtidbwtidbwtidb.tidbmtidbytidbstidbqtidbltidb.tidbctidbotidbmtidb |
+-----------------------------------------------------------------------+
1 row in set (0.01 sec)
But the correct result should be:
+-----------------------------------------------------------------------+
| REPLACE('www.mysql.com', '', 'tidb') |
+-----------------------------------------------------------------------+
| www.mysql.com |
+-----------------------------------------------------------------------+
1 row in set (0.01 sec)