第二章 单表查询
T-SQL
use TSQL2012
--Order by
select empid, firstname, lastname, country
from HR.Employees
order by hiredate
--Top
select top(5) orderid, orderdate, custid, empid
from sales.orders
order by orderdate desc;
--Top Percent
select top(1) percent orderid, orderdate, custid, empid
from sales.orders
order by orderdate desc;
--Top With Ties
select top(5) with ties orderid, orderdate, custid, empid
from sales.orders
order by orderdate desc;
--Over Partition By
Select orderid,
custid,
val,
sum(val) over() as totalvalue,
sum(val) over(partition by custid) as custtotalvalue,
count(custid) over(partition by custid) as custtotalorders
from sales.ordervalues;
--Over
select orderid, custid, val,
100. * val / sum(val) over() as pctall,
100. * val / sum(val) over(partition by custid) as pctcust
from sales.ordervalues;
--Over Row_Number Rank Dense_Rank Ntile
select top(10) orderid, custid, val,
Row_Number() over(order by val) as rownum,
rank() over(order by val) as val_rank,
dense_rank() over(order by val) as val_dense_rank,
ntile(300) over(order by val) as val_ntile
from sales.ordervalues
order by val;
--Over Row_Number
select orderid, custid, val,
row_Number() over(partition by custid order by val) as rownum
from sales.ordervalues
order by custid, val;
--Distinct Over
select distinct val, row_number() over(order by val) as rownum
from sales.ordervalues;
--group by over
select val, row_number() over(order by val) as rownum
from sales.ordervalues
group by val;
--In
select orderid, empid, orderdate
from sales.orders
where orderid in (10248, 10249, 10250);
--Between
select orderid, empid, orderdate
from sales.orders
where orderid between 10300 and 10310;
--Like
Select empid, firstname, lastname
from hr.employees
where lastname like N'D%'
--*
select orderid, productid, qty, unitprice, discount,
qty*unitprice*(1-discount) as val
from sales.orderdetails
--Case
select productid, productname, categoryid,
case categoryid
when 1 then 'First'
when 2 then 'Second'
when 3 then 'Third'
else 'Unknown'
end as categoryname
from production.products;
--ntile top case
select top(10) orderid, custid, val,
case ntile(250) over(order by val)
when 1 then 'low'
when 2 then 'Medium'
when 3 then 'High'
end as titledesc
from sales.ordervalues
order by val;
--case
select orderid, custid, val,
case
when val < 1000.00 then 'Less than 1000'
when val between 1000.00 and 3000.00 then 'Between 1000 and 3000'
when val >3000.00 then 'More than 3000'
else 'Unknown'
end as valuecategory
from sales.ordervalues;
--is null
--"= null" is different from "is null"
select custid, country, region, city
from sales.customers
where region is null;
--<> is null
select custid, country, region, city
from sales.customers
where region is null or region <> N'WA'
select empid, firstname, lastname
from hr.employees
where lastname = N'davis';
-- +
select empid, firstname + N' ' + lastname as fullname
from hr.employees;
set concat_null_yields_null off;
-- + null
Select custid, country, region, city,
country + N',' + region + N',' + city as location
from sales.customers;
set concat_null_yields_null on;
--coalesce
select custid, country, region, city,
country + N',' + coalesce(region, N'$$$$$$') + N',' + city as location
from sales.customers;
--substring
select substring(N'abcdefg', 1, 3) as abc;
--left
select left(N'abcdefg', 3) as abc;
--right
select right(N'abcdefg', 4) as defg;
--len result:11
select len(N' abcdefg ') as str_length;
--datalength result:30
select datalength(N' abcdefg ') as str_datalength;
--charindex result:6, 14
select charindex(' ', 'Itzik Ben-Gan ') as idx;
select charindex(' ', 'Itzik Ben-Gan ', 7) as idx;
--patindex
select patindex('%[0-9]%', 'abcd123efgh') as idx;
--replace
select replace('1-A 2-B', '-', ':') as string;
select empid, lastname,
len(lastname)- len(replace(lastname, 'e', '')) as numoccur
from hr.employees;
--replicate
select replicate(N'abc',2) as abcabc;
select supplierid,
right(replicate('0', 9) + cast(supplierid as varchar(10)),10) as strsupplierid
from production.suppliers;
--stuff
select stuff('xyz', 2, 1, 'abc') as xabcz;
--upper
select upper('Itzik Ben-Gan') as name;
--lower
select lower('Itzik Ben-Gan') as name;
--rtrim
select rtrim(' abc ') as newstr;
--ltrim
select ltrim(' abc ') as newstr;
-- %
select empid, lastname
from hr.employees
where lastname like N'D%';
-- _
select empid, lastname
from hr.employees
where lastname like N'_e%'
-- []
select empid, lastname
from hr.employees
where lastname like N'[ABC]%'
-- [ - ]
select empid, lastname
from hr.employees
where lastname like N'[A-E]%'
-- [^ - ]
select empid, lastname
from hr.employees
where lastname like N'[^A-E]%'
select
getdate() as [GETDATE],
current_timestamp as [CURRENT_TIMESTAMP],
GETUTCDATE() AS [GETUTCDATE],
sysdatetime() as [SYSDATETIME],
sysutcdatetime() as [SYSUTCDATETIME],
SYSDATETIMEOFFSET() AS [SYSDATETIMEOFFSET];
--CAST
select cast('20090212' as date) as currentdate;
--convert
select convert(char(8), current_timestamp, 112) as [datetime] ;
--day month year
select
day('20090212') as theday,
month('20090212') as themonth,
year('20090212') as theyear;
exec sys.sp_tables;