MAKE_SET(bits,str1,str2,...)
返回一个设定值(含子字符串分隔字符串。，。字符)由那些在设置位的相应位的字符串。str1对应于位0，str2至位1，以此类推。NULL值在str1，str2，...不添加到结果。
SQL> SELECT MAKE_SET(1,'a','b','c'); +---------------------------------------------------------+ | MAKE_SET(1,'a','b','c') | +---------------------------------------------------------+ | a | +---------------------------------------------------------+ 1 row in set (0.00 sec)
