show use T select ###1,###2,###3 조회할 필드 선택 from T limit #; 조회할 데이터의 숫자를 제한 select distinct ### 중복 데이터를 제거할 수 있다. select ###, count(###) count로 개수를 조회할 수 있음 from T group by ###; ㅎ select count(*) from session where ### = 조건; select distinct ###, 필드 값의 변환을 위해 case when ### in (1,2,3) then 'A표현' if else 처럼 사용할 수 있다. when ### in (4,5,6) then 'B표현' Else 'C표현' end 표현할 필드네임, count(*) from T group by ###; - NULL 표현 TwithNull = null이 포함된 테이블 select count(1) from TwithNull; NULL 포함됌 select count(0) from TwithNull; NULL 포함됌 select count(null) from TwithNull; 0 select count(value) from TwithNull; NULL 포함 안됌. select count(distinct value) from TwithNull; NULL 포함 안됌. select count(###) from T where (###) in (1,2,3); select count(###) from T where ### like '%포함될_데이터%'; select distinct (###) from T where (###) not like '%포함안될_데이터%'; select length((###)), upper((###)), lower((###)), left((###),4), rpad((###),15,'-'), lpad((###),15,'-') from T; select ### from T order by ### desc(asc); select #time#, convert_tz(#time#, 'GMT','Asia/Seoul') seoul_time, year(#time#) y, quarter(#time#) q, month(#time#) m , monthname(#time#) mnn, date(#time#) d, hour(#time#) h, minute(##time#) m, second(#time#) s from T; select #time#, now(), datediff(now(), #time#) gap_in_days, date_add(#time#, interval 10 day) ten_days_after_created from T; select str_to_date('01,5,2013','%d,%m,%y'); select cast('100.0' as float), convert('100.0',float); select left(#time#, 7) as mon, count(mon) as session_count from T group by mon order by mon; select ###1, count(###1) as session_Count, count(distinct ###2) as user_count from T group by ###1 order by session_Count desc; select ###1, count(###1) as session_Count from T group by ###1 order by session_Count desc limit 1; select left(#time#, 7) as mon, count(distinct ###) as user_count from T group by mon order by mon; select s.id, s.user_id, s.created, s.channel_id, c.channel from T1 s join T2 c on c.id = s.channel_id; select left(#time#, 7) as mon, c.channel, count(distinct ###) as mau from T1 s join T3 c on c.id = s.channel_id group by 1,2 order by 1 desc, 2;