各位大侠帮小弟我看看这是哪错了急

各位大侠帮我看看这是哪错了急！
sql = "insert into"+ dbStat +"s50ewtbuyring (id, usernumber, opertime, ringtype, ringfee)"+
 " values(SEQ_STATOPLOG.NEXTVAL,'"+userNumber+"',"+to_char(sysdate,'YYYY.MM.DD HH24:MI:SS')+","+ringType+","+ringfee;

这里面的to_char哪有写错吗怎么在java里提示Invalid character constant这个错误

[解决办法]
sql = "insert into"+ dbStat +"s50ewtbuyring (id, usernumber, opertime, ringtype, ringfee)"+
" values(SEQ_STATOPLOG.NEXTVAL,'"+userNumber+"',"+"to_char(sysdate,'YYYY.MM.DD HH24:MI:SS')+"+","+ringType+","+ringfee;