Chapter IV Data Query (on)

check sentence:

select <column name> 

from <表名>

[Where <query expression>]

[Order by <sorted column name> [asc or desc]]

　　asc ascending (default)  

　　desc Descending

Using a column named as (alias)

Scode the SELECT AS student numbers, Sname as student names, Saddress as student address

from students

where Saddress <> 'Xinxiang'

 

select FirstName + '.' + LastName AS '姓名' from Employees

 

 

Queries blank line

select SName from students where Semail IS NULL

 

Queries non-blank line

select sname from students where not semail is null

or

select sname from students where semail is  not   null

 

Limit the number of fixed lines

select top 5 sname, saddress 

from students where ssex = 0

 

What percentage of the return line

select top 20 percent sname, saddress 

from students where ssex = 0