03_where조건절

use mydb

select top 5 *
from tb_test
order by ubirth desc

문)수당제일 많이 받는 사람?
select top 1 uname
from tb_test
order by umoney desc

Select * from tb_test

select top 2 *
from tb_test
where uaddress='서울'
order by uage

select *
from tb_test
where uaddress='서울'
and uage>=30

select *
from tb_test
where uage>=20
and uage<=29

select * from tb_test where uage not between 20 and 29

select *
from tb_test
where uaddress='서울'
or uaddress='부산'

select *
from tb_test
where uaddress not in ('서울','부산')

insert into tb_test(uid,uname,uage,ubirth)
values('song3','코스모스',44,'1990-2-20')

[NULL]관련..
1.SQL에서는 비어있는 값을 NULL이란 키워드로 채움.
2.NULL은 값이 없는 공허한(비어있는)상태를 의미.
3.데이터가 없는곳(셀부분)을 DBMS가 비워두기 어색하니깐
   NULL이란 키워드를 사용해서 표현해준것 뿐.
4.조건식에서 where umoney='' 가 아니라
   where umoney is null / umoney is not null
5. SQL에서 함수연산을 할 경우 NULL은 제외된다.
select *
from tb_test
where umoney is null

select *
from tb_test
where umoney is not null

갯수count()
합계sum()
평균avg()
최대값max()
최소값min()

select avg(uage) as [나이평균],
max(uage) as [최대나이],
min(uage) as [최소나이]
from tb_test

select * from tb_test

select count(uname),count(uaddress),count(*)
from tb_test
select *
from tb_test
where uname like '__민_'

select *
from tb_test
where uname like '민_'

select *
from tb_test
where uname like '_민'

update tb_test
set uaddress='seoul'
where uaddress='서울'
문)영문s만 대문자로 바꾸시오. seoul -> Seoul
update tb_test
set uaddress='Seoul'
where uaddress='seoul'

문)현재수당에 500원씩 더 추가하시오
update tb_test
set umoney=umoney+500

begin tran
delete from tb_test
rollback