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select floor(regno/100) "groupby", min(regno),max(regno),min(name),max
+(name) 
from registrations 
group by `groupby`;

set @rownum := 0;
select floor(@rownum  := @rownum + 0.01) "set_num", min(lname),max(lna
+me) 
from (select * from registrants order by lname) reg 
group by "set_num";