USE tpch1;
select case substr(dtm,12,2) when '06' then 'L' when '08' then 'M' end daypart, count(*)
from dtypes group by 1 order by 1;
daypart	count(*)
NULL	60
L	20
M	20
select case substr(dtm,12,2) when '06' then 'L' when '08' then 'M' else 'Z' end daypart, count(*)
from dtypes group by 1 order by 1;
daypart	count(*)
L	20
M	20
Z	60
select substr(dtm,12,2), case substr(dtm,12,2) when '06' then 'L' when '08' then 'M' end daypart, count(*)
from dtypes group by 1,2 order by 1;
substr(dtm,12,2)	daypart	count(*)
06	L	20
07	NULL	60
08	M	20
select substr(dtm,12,2), case substr(dtm,12,2) when '06' then 'L' when '08' then 'M' else 'Z' end daypart, count(*)
from dtypes group by 1,2 order by 1;
substr(dtm,12,2)	daypart	count(*)
06	L	20
07	Z	60
08	M	20