select empid,custid,SUM(qty) as sumqty 
from dbo.Orders
group by empid,custid;

--1.1标准SQL透视转换
select empid,
    SUM(case when custid=‘A‘ then qty end) as A,
    SUM(case when custid=‘B‘ then qty end) as B,
    SUM(case when custid=‘C‘ then qty end) as C,
    SUM(case when custid=‘D‘ then qty end) as D
from dbo.Orders
group by empid;

select empid,A,B,C,D
from (select empid,custid,qty
      from dbo.Orders) as D
  pivot (sum(qty) for custid in (A,B,C,D)) as P;

select *
from (select empid, custid,
        case custid
            when ‘A‘ then A
            when ‘B‘ then B
            when ‘C‘ then C
            when ‘D‘ then D
        end as qty
      from dbo.EmpCustOrders
        cross join (VALUES(‘A‘),(‘B‘),(‘C‘),(‘D‘)) as Custs(custid)) as D
where qty is not null;

select empid, custid, qty
from dbo.EmpCustOrders
  unpivot (qty for custid in (A,B,C,D)) as U;

--3.1GROUPING SETS从属子句
select empid,custid,SUM(qty) as sumqty
from dbo.Orders
group by 
  GROUPING SETS
  (
    (empid,custid),
    (empid),
    (custid),
    ()
   );

--3.2CUEE从属子句
select empid,custid,SUM(qty) as sumqty
from dbo.Orders
group by cube(empid,custid);

--3.3ROLLUP从属子句
select
  YEAR(orderdate) as orderyear,
  MONTH(orderdate) as ordermonth,
  DAY(orderdate) as orderday,
  SUM(qty) as sumqty
from dbo.Orders
group by rollup(YEAR(orderdate),MONTH(orderdate),DAY(orderdate));

INSERT INTO dbo.Orders(orderid, orderdate, empid, custid)
  VALUES(10001, ‘20090212‘, 3, ‘A‘);

INSERT INTO dbo.Orders(orderid, orderdate, empid, custid)
  SELECT orderid, orderdate, empid, custid
  FROM TSQLFundamentals2008.Sales.Orders
  WHERE shipcountry = ‘UK‘;

INSERT INTO dbo.Orders(orderid, orderdate, empid, custid)
  EXEC TSQLFundamentals2008.Sales.usp_getorders @country = ‘France‘;

--保证目标表不存在
IF OBJECT_ID(‘dbo.Orders‘, ‘U‘) IS NOT NULL DROP TABLE dbo.Orders;

SELECT orderid, orderdate, empid, custid
INTO dbo.Orders
FROM TSQLFundamentals2008.Sales.Orders;

BULK INSERT dbo.Orders FROM ‘C:\testdata\orders.txt‘
  WITH 
    (
       DATAFILETYPE    = ‘char‘,
       FIELDTERMINATOR = ‘,‘,
       ROWTERMINATOR   = ‘\n‘
    );

DELETE FROM dbo.Orders
WHERE orderdate < ‘20070101‘;

DELETE FROM O
FROM dbo.Orders AS O
  JOIN dbo.Customers AS C
    ON O.custid = C.custid
WHERE C.country = N‘USA‘;

DELETE FROM dbo.Orders
WHERE EXISTS
  (SELECT *
   FROM dbo.Customers AS C
   WHERE Orders.custid = C.custid
     AND C.country = N‘USA‘);

UPDATE dbo.T1
  SET col1 = col1 + 10, col2 = col1 + 10;

UPDATE dbo.T1
  SET col1 = col2, col2 = col1;

UPDATE OD
  SET discount = discount + 0.05
FROM dbo.OrderDetails AS OD
  JOIN dbo.Orders AS O
    ON OD.orderid = O.orderid
WHERE custid = 1;

UPDATE dbo.OrderDetails
  SET discount = discount + 0.05
WHERE EXISTS
  (SELECT * FROM dbo.Orders AS O
   WHERE O.orderid = OrderDetails.orderid
     AND custid = 1);

DECLARE @nextval AS INT;
UPDATE Sequence SET @nextval = val = val + 1;
SELECT @nextval;

MERGE INTO dbo.Customers AS TGT
USING dbo.CustomersStage AS SRC
  ON TGT.custid = SRC.custid
WHEN MATCHED THEN
  UPDATE SET
    TGT.companyname = SRC.companyname,
    TGT.phone = SRC.phone,
    TGT.address = SRC.address
WHEN NOT MATCHED THEN 
  INSERT (custid, companyname, phone, address)
  VALUES (SRC.custid, SRC.companyname, SRC.phone, SRC.address);

-- 基于联接的UPDATE
UPDATE OD
  SET discount = discount + 0.05
FROM dbo.OrderDetails AS OD
  JOIN dbo.Orders AS O
    ON OD.orderid = O.orderid
WHERE custid = 1;
-- 基于表表达式（这里是CTE）的UPDATE
WITH C AS
(
  SELECT custid, OD.orderid,
    productid, discount, discount + 0.05 AS newdiscount
  FROM dbo.OrderDetails AS OD
    JOIN dbo.Orders AS O
      ON OD.orderid = O.orderid
  WHERE custid = 1
)
UPDATE C
  SET discount = newdiscount;

-- 删除前50行
DELETE TOP(50) FROM dbo.Orders;
-- 更新前50行
UPDATE TOP(50) dbo.Orders
  SET freight = freight + 10.00;
-- 基于CTE删除前50行
WITH C AS
(
  SELECT TOP(50) *
  FROM dbo.Orders
  ORDER BY orderid
)
DELETE FROM C;
-- 基于CTE更新前50行
WITH C AS
(
  SELECT TOP(50) *
  FROM dbo.Orders
  ORDER BY orderid DESC
)
UPDATE C
  SET freight = freight + 10.00;

INSERT INTO dbo.T1(datacol)
  OUTPUT inserted.keycol, inserted.datacol
    SELECT lastname
    FROM TSQLFundamentals2008.HR.Employees
    WHERE country = N‘USA‘;

DELETE FROM dbo.Orders
  OUTPUT
    deleted.orderid,
    deleted.orderdate,
    deleted.empid,
    deleted.custid
WHERE orderdate < ‘20080101‘;

UPDATE dbo.OrderDetails
  SET discount = discount + 0.05
OUTPUT
  inserted.productid,
  deleted.discount AS olddiscount,
  inserted.discount AS newdiscount
WHERE productid = 51;

MERGE INTO dbo.Customers AS TGT
USING dbo.CustomersStage AS SRC
  ON TGT.custid = SRC.custid
WHEN MATCHED THEN
  UPDATE SET
    TGT.companyname = SRC.companyname,
    TGT.phone = SRC.phone,
    TGT.address = SRC.address
WHEN NOT MATCHED THEN 
  INSERT (custid, companyname, phone, address)
  VALUES (SRC.custid, SRC.companyname, SRC.phone, SRC.address)
OUTPUT $action, inserted.custid,
  deleted.companyname AS oldcompanyname,
  inserted.companyname AS newcompanyname,
  deleted.phone AS oldphone,
  inserted.phone AS newphone,
  deleted.address AS oldaddress,
  inserted.address AS newaddress;

--set方式
declare @i as int
set @i=10;

--SQL Server 2008可以在同一语句同时声明和初始化变量
declare @i as int = 10;

--select方式
declare @firstname as nvarchar(20), @lastname as nvarchar(40);

select
  @firstname = firstname,
  @lastname = lastname
from hr.Employees
where empid=3;

select @firstname as firstname, @lastname as lastname;

--set比select语句更安全
declare @empname as nvarchar(61);

set @empname = (select firstname + N‘ ‘+ lastname
                from hr.Employees
                where mgrid=2);
                
select @empname as empname;

-- A Batch as a Unit of Parsing
-- Valid batch
PRINT ‘First batch‘;
USE TSQLFundamentals2008;
GO
-- Invalid batch
PRINT ‘Second batch‘;
SELECT custid FROM Sales.Customers;
SELECT orderid FOM Sales.Orders; -- 这一句有语法错误，故整个批处理不能提交到SQL Server执行
GO
-- Valid batch
PRINT ‘Third batch‘;
SELECT empid FROM HR.Employees;
GO

IF DAY(CURRENT_TIMESTAMP) = 1
BEGIN
  PRINT ‘Today is the first day of the month.‘;
  PRINT ‘Starting a full database backup.‘;
  BACKUP DATABASE TSQLFundamentals2008
    TO DISK = ‘C:\Temp\TSQLFundamentals2008_Full.BAK‘ WITH INIT;
  PRINT ‘Finished full database backup.‘;
END
ELSE
BEGIN
  PRINT ‘Today is not the first day of the month.‘
  PRINT ‘Starting a differential database backup.‘;
  BACKUP DATABASE TSQLFundamentals2008
    TO DISK = ‘C:\Temp\TSQLFundamentals2008_Diff.BAK‘ WITH INIT;
  PRINT ‘Finished differential database backup.‘;
END
GO

DECLARE @i AS INT;
SET @i = 1;
WHILE @i <= 10
BEGIN
  PRINT @i;
  SET @i = @i + 1;
END;
GO

-- Example: Running Aggregations
SET NOCOUNT ON;
USE TSQLFundamentals2008;

DECLARE @Result TABLE
(
  custid     INT,
  ordermonth DATETIME,
  qty        INT, 
  runqty     INT,
  PRIMARY KEY(custid, ordermonth)
);

DECLARE
  @custid     AS INT,
  @prvcustid  AS INT,
  @ordermonth DATETIME,
  @qty        AS INT,
  @runqty     AS INT;

DECLARE C CURSOR FAST_FORWARD /* read only, forward only */ FOR
  SELECT custid, ordermonth, qty
  FROM Sales.CustOrders
  ORDER BY custid, ordermonth;

OPEN C

FETCH NEXT FROM C INTO @custid, @ordermonth, @qty;

SELECT @prvcustid = @custid, @runqty = 0;

WHILE @@FETCH_STATUS = 0
BEGIN
  IF @custid <> @prvcustid
    SELECT @prvcustid = @custid, @runqty = 0;

  SET @runqty = @runqty + @qty;

  INSERT INTO @Result VALUES(@custid, @ordermonth, @qty, @runqty);
  
  FETCH NEXT FROM C INTO @custid, @ordermonth, @qty;
END

CLOSE C;

DEALLOCATE C;

SELECT 
  custid,
  CONVERT(VARCHAR(7), ordermonth, 121) AS ordermonth,
  qty,
  runqty
FROM @Result
ORDER BY custid, ordermonth;
GO

BEGIN TRY
  PRINT 10/2;
  PRINT ‘No error‘;
END TRY
BEGIN CATCH
  PRINT ‘Error‘;
END CATCH
GO