basic frequent Sql commends in sql server

description: sql comments for basic query
-- use 
use testdb
go 

select * from people
select top 1 * from people

-- insert into people values (1, 'lily', 'f', 12)
-- insert into people values (2, 'chao', 'm', 16)
-- insert into people values (3, 'alin', 'f',null)

select id, name from people

-- order by
select name, age from people 
order by age desc,id

-- order by number
select name, age from people 
order by 2 --2 means age 

-- isnull()
select name, ISNULL (age, '') from people

--alias
select name, ISNULL (age, '') as a from people

-- concat strings 
select 'people ' + TRIM (name) + ' is age of ' + convert(varchar, isnull(age, '')) as [description] 
from people

-- round()
select age, age * 10 as 'age10',
round(convert(float,age)/8, 1) as 'ageD8',
round(age/3, 0) as 'ageD3'
from people

-- where 
select * from people 
where age <> 12

-- and or 
-- select date from time where data between '2005-10-10' and '1/1/2006'
select * from people where id = 2 or id = 3
select * from people where name = 'chao' and age =16

-- wildcard % like 
select * from people where name like '%h%' 

-- _ single character 
select * from people where name like '_hao%'

-- in 
select * from people
where age in (14,16)

-- not in 
select * from people 
where age not in (16)

-- is null
select * from people 
where age is null

-- is not null 
select * from people 
where age is not null