substring(? from 1 for length(phonenum))是什么意思啊?
StringBuffer sql = new StringBuffer();
sql.append("select * from ");
sql.append(TableDef.IIP_NUMTABMOB);
sql.append(" where substring(? from 1 for length(phonenum)) = phonenum");
dbf = new SqlDB();
dbf.setSql(sql.toString());
dbf.setString(1, phonenum);
sqlrs = dbf.executeQuery();
意思大概我能猜到,关键是请问substring(? from 1 for length(phonenum)这个SQL语句语法是什么?