Ngn ng lp trnh Transaction SQL

Ni dung bi hc

1. Enterprise Application Architechter

2. Bin v cc kiu d liu

3. Ton t

4. Hm

5. Cc cu lnh iu khin

6. Cc cch s dng cc lnh T-SQL

7. Stored Procedure

8. Trigger

Thit k Enterprise Application Architecture

Xc nh cc lp logical (Logical Layers)

Thit k cc lp vt l (Physical Layers)

Truy xut d liu

Logical Layers

Data presentation Layer

c xem l user service and cho php user xem v thao tc ln data: web browser and cc Microsoft Windows applications

S dng cc service m application logic layer cung cp

Application Logic Layer Cha application logic, nh ngha cc rules v

processes gip cho user khng cn truy xut trc tip vo database

Clients kt ni vo business service kt ni vo data server. Business service l cc custom-built components hoc integrated applications v services, v d nh Web services.

Application logic layer cha cc components to thnh transaction services, messaging services, hoc object v connection management services.

Data Services Layer

Data services bao gm data access logic v data storage.

Bao gm cc SQL Server stored procedures qun l data traffic v integrity trn the database server.

Thit k cc lp vt l

Truy xut d liu

Khai bo bin

Dng t kho declare khai bo bin

DECLARE {@local_variable data_type} [,...n]

Gn gi tr cho bin

SET @local_variable_name = expression

V d

DECLARE @vLastName char(20),

@vFirstName varchar(11)

SET @vLastName = 'Dodsworth

SELECT @vFirstName = FirstName

FROM Northwind.Employees

WHERE LastName = @vLastName

PRINT @vFirstName + ' ' + @vLastName

Gn gi tr cho

bin bng t kho set

hoc bng cu lnh select

Data Type (1) Integers

Bigint: 8 bytes Int: 4 bytes Smallint: 2 bytes Tinyint: 1 byte, t 0 -> 255.

bit Bit: 1 hoc 0 value.

decimal and numeric Decimal t -10^38+1->10^38 1. Numeric: ging decimal.

money and smallmoney Money: 8 bytes Smallmoney: 4 bytes

Approximate Numerics Float: t -1.79E + 308 -> 1.79E + 308. Real: t -3.40E + 38 -> 3.40E + 38.

Data Type (2) datetime and smalldatetime

Datetime: t 1/1/1753-> 31/12/9999.

Smalldatetime t 1/1/1900, -> 6/6/2079.

Character Strings

Char: Fixed-length non-Unicode character,

Ton t (operators)

Cc loi ton t

S hc: *, /, %, - , +

So snh: =, , >, >=,

Th t u tin cc ton t

Functions (1)

Aggregate functions: tnh ton trn mt nhm v tr v mt gi tr. V d:

SELECT AVG(UnitPrice) FROM Products

Products

28.8663

(1 row(s) affected)

Functions (2)

Scalar functions: Tc ng ln mt gi tr v tr v mt gi tr. C th s dng hm trong cc biu thc.

Chng ta c th nhm cc scalar function theo nhm sau:

Configuration Tr v cc thng tin v configuration

Cursor Tr v cc thng tin v Cursor

DateTime Hm tc ng ln gi tr dateTime nhp vo v tr v mt gi tr l string, numeric, hoc datetime

Mathematical Hm s hc

Metadata Thng tin v database

String Cc hm chui

Functions (3)_ V d

SELECT DB_NAME() AS 'database'

Database

Northwind

(1 row(s) affected)

SET DATEFORMAT dmy

GO

DECLARE @vdate datetime

SET @vdate = '29/11/00'

SELECT @vdate

2000-11-29 00:00:00.000

Mathematical Functions

ABS DEGREES RAND

ACOS EXP ROUND

ASIN FLOOR SIGN

ATAN LOG SIN

ATN2 LOG10 SQUARE

CEILING PI SQRT

COS POWER TAN

COT RADIANS

Aggregate Functions

AVG MAX

BINARY_CHECKSUM MIN

CHECKSUM SUM

CHECKSUM_AGG STDEV

COUNT STDEVP

COUNT_BIG VAR

GROUPING VARP

DateTime functions Function Determinism

DATEADD Deterministic

DATEDIFF Deterministic

DATENAME Nondeterministic

DATEPART Deterministic except when used as DATEPART (dw, date). dw, the weekday datepart, depends on the value set by SET DATEFIRST, which sets the first day of the week.

DAY Deterministic

GETDATE Nondeterministic

GETUTCDATE Nondeterministic

MONTH Deterministic

YEAR Deterministic

String functions

ASCII NCHAR SOUNDEX

CHAR PATINDEX SPACE

CHARINDEX REPLACE STR

DIFFERENCE QUOTENAME STUFF

LEFT REPLICATE SUBSTRING

LEN REVERSE UNICODE

LOWER RIGHT UPPER

LTRIM RTRIM

Cast v Convert

CAST ( expression AS data_type )

CONVERT ( data_type [ ( length ) ] , expression [ , style ] )

Control-of-Flow Language

1. BEGIN...END : nh ngha mt khi lnh

BEGIN sql_statement | statement_block

END

2. If .. else IF Boolean_expression

{ sql_statement | statement_block } [ ELSE { sql_statement | statement_block } ]

if (select count(*) from customers where country='canada') > 0

begin

print There are many Canada customers'

end

else

print Welcome'

V d lnh If. Else USE Northwind

IF EXISTS (SELECT OrderID FROM Orders

WHERE CustomerID = 'Frank')

PRINT '*** Customer cannot be deleted ***'

ELSE

BEGIN

DELETE Customers WHERE CustomerID = 'Frank'

PRINT '*** Customer deleted ***'

END

3. While WHILE Boolean_expression

{ sql_statement | statement_block } [ BREAK ] { sql_statement | statement_block } [ CONTINUE ]

BREAK: thot ra khi vng while

CONTINUE: restart li vng lp, b qua cc lnh sau CONTINUE.

GOTO

GOTO LabelName

IF (SELECT SYSTEM_USER()) = 'payroll'

GOTO calculate_salary

-- Other program code would appear here.

-- When the IF statement evaluates to TRUE,

-- the statements between the GOTO and

-- the calculate_salary label are ignored.

-- When the IF statement evaluates to FALSE the

-- statements following the GOTO are executed.

calculate_salary:

-- Statements to calculate a salary would appear after the label.

Row .Level Simple CASE function: CASE input_expression

WHEN when_expression THEN result_expression [ ...n ] [ ELSE else_result_expression ] END

Searched CASE function:

CASE WHEN Boolean_expression THEN result_expression [ ...n ] [ ELSE else_result_expression ] END

V d SELECT ProductID, 'Product Inventory Status' =

CASE

WHEN (UnitsInStock < UnitsOnOrder AND Discontinued = 0)

THEN 'Negative Inventory - Order Now!'

WHEN ((UnitsInStock-UnitsOnOrder) < ReorderLevel AND Discontinued = 0)

THEN 'Reorder level reached- Place Order'

WHEN (Discontinued = 1) THEN '***Discontinued***'

ELSE 'In Stock'

END

FROM Products

Kt qu cu lnh

p dng trong database QLVT

Lit k cc chi tit ho n ca ho n HD01 gm cc thng tin: M vt t, SL, Gi bn, KM vi

KM = 0 nu SL =10

KM = (SL*giaban) * 0.2 nu SL >=100

Comments Inline comments SELECT ProductName,

(UnitsInStock + UnitsOnOrder) AS Max, -- Calculates inventory

SupplierID

FROM Products

SELECT

Block comments /*

** This code retrieves all rows of the products table

** and displays the unit price, the unit price increased

** by 10 percent, and the name of the product.

*/

SELECT UnitPrice, (UnitPrice * 1.1), ProductName FROM Products

Lnh RAISERROR

Tr v mt thng bo li do user nh ngha

C php:

RAISERROR ( { msg_id | msg_str }

{ , severity , state } ) [ WITH option [ ,...n ] ]

Tham s

msg_id l m li c lu trong sysmessages table.

msg_str: l chui thng bo li c nh dng ging nh lnh printf trong lp trnh C

Severity: mc nghim trng ca li. C gi tr t 0->18 c dng bi user, t 19 -> 25 c dng bi sysadmin (dng vi WITH LOG).

State: s nguyn t 1 ->127 m t mc cn thit ca li.

Cc cch thc hin cc lnh T-SQL

Cc lnh c cu trc ng

Dng Batch

Dng Scripts

Dng Transactions

Dng XML

Dng cu trc lnh ng

Dng lnh EXECUTE vi cc hng chui v bin

S dng khi ta phi gn gi tr cho bin ti thi im execute

Cc bin v table tm ch tn ti trong thi gian thc thi lnh.

DECLARE @dbname varchar(30), @tblname varchar(30)

SET @dbname = 'Northwind'

SET @tblname = 'Products'

EXECUTE

('USE ' + @dbname + ' SELECT * FROM '+ @tblname)

S dng khi (batch)

Mt hoc nhiu lnh T- SQL c submit cng lc vi nhau.

S dng lnh GO kt thc mt khi

Cc bin khng th tham chiu sau lnh GO

Khng th dng cc lnh sau y trong batch:

CREATE PROCEDURE

CREATE VIEW

CREATE TRIGGER

CREATE RULE

CREATE DEFAULT

V d lnh khi lnh batch hp l

CREATE DATABASE ...

CREATE TABLE ...

GO

CREATE VIEW1 ...

GO

CREATE VIEW2 ...

GO

CREATE DATABASE ...

CREATE TABLE ...

CREATE TRIGGER ...

CREATE TRIGGER ...

GO

S dng script

Script l mt tp tin c phn m rng l .sql, c ni dung l cc lnh T-SQL, c to bi bt k mt Text editor no.

c thc hin trong cng c SQL Query Analyzer hoc osql Utility

c dng li khi cn.

Dng Transactions

c x l ging mt Batch Bo m tnh ton vn d liu Ton b cc lnh trong transaction s thnh cng hoc khng

thnh cng Mt transaction c th c nhiu batch Transaction c bt u bng lnh BEGIN TRANSACTION V kt thc bng lnh COMMIT TRANSACTION Hoc ROLLBACK TRANSACTION

V d transaction trong database QLVT

BEGIN TRANSACTION insert into chitiethoadon values ('hd001','vt03',50,null,30000) IF @@ERROR 0 BEGIN RAISERROR ('Transaction not completed.', 16, -1) ROLLBACK TRANSACTION END update vattu set slton = slton-50 where mavt='vt03' IF @@ERROR 0 BEGIN RAISERROR ('Transaction not completed.', 16, -1) ROLLBACK TRANSACTION END COMMIT TRANSACTION

Dng XML

Cho php Client Browser nh dng d liu:Dng mnh FOR XML trong lnh SELECT tr kt qu dng XML

Dng FOR XML AUTO

Hoc FOR XML RAW

Khi dng mnh FOR XML trong lnh SELECT, ta khng th dng: Lnh SELECT lng nhau

Mnh INTO .

Mnh COMPUTE BY.

Dng Stored procedures m c gi trong lnh INSERT

nh ngha view hoc user-defined function tr v mt rowset.

V d dng XML (1) Use QLVT

SELECT makh, tenkh FROM khachhang

FOR XML AUTO

Dng XML (2) Use QLVT

SELECT makh, tenkh FROM khachhang

FOR XML RAW

Dng database QLVT Vit mt on m lnh cho bit tng tr gi ca tt c cc ho

n ca khch hng c m l KH01 trong nm 2000 vi kt qu tr v

Khch hng KH01 c tng tr gi cc ho n l

Nu Khch hng khng c ho n no th in ra chui:

Khch hng ny khng mua hng trong nm 2000

declare @tg int

select @tg=sum(sl*giaban)

from chitiethoadon as cthd, hoadon as hd

where cthd.mahd = hd.mahd and hd.makh='kh01 and year(ngay)=2000

if @tg>0

print 'Khach hang kh01 co tong tri gia ' + str(@tg,10)

else

print 'Khach hang chua mua hang'

Dng database QLDIEM

Lit k danh sch cc sinh vin gm cc thng tin: MASV, HOTEN, NGAYSINH, PHAI (NU hoc NAM) ca nhng sinh vin c tui ln hn hoc bng 20.

Khai bo mt bin n cha s lng cc chi tiet ho n c trong table cthd ca ho n hd001. Nu n=0 th xo ho n c m l hd001 trong table ho n, ngc li th xut ra thng bo li Hoa don nay khong xoa duoc

Hy thc hin cc lnh xo mt ho n c m hd l hd001. nu ho n hd001 c chi tit ho n th phi xo cc chi tit ho n ca hd ny trc. Cc lnh ny phi hon thnh hon ton.

Ly ra danh sch cc ho n c tng tr gi ln nht

Ly ra cc khch hng mua nhng mt hng m khch hng kh01 mua.

Tnh s lng ho n ca 2 khch hng KH01 v KH02 v in ra kt qu so snh 2 s lng ho n ny

Stored Procedure

Mc tiu bi hc

Hiu c stored procedure l g, procedure hot ng nh th no.

Qun l procedure: To, xo, sa v thc thi

Tham s trong store procedure

Bi tp p dng

Ni dung bi hc

1. Gii thiu Stored procedures

2. To, thc thi, cp nht v xo stored procedures

3. Bi tp thc hnh

4. Truyn tham s trong stored procedures

5. iu khin li

6. Mt s lu

Gii thiu Stored Procedure (1)

Stored procedure l mt tp cc lnh Transact SQL c t tn v lu tr trong database server

C th nhn tham s vo v tham s tr gi tr v

Tr v trng thi thc thi ca procedure l thnh cng hay khng thnh cng

Gii thiu Stored Procedure (2)

C 5 loi stored procedure: System (sp_): c trong master database, c truy xut t bt k

mt database no, nhm cung cp cc thng tin system catalog hoc thc hin cc nhim v ca administration.

Local : c to t user

Temporary: c tn bt u bng # (local) hoc ## (global). Khng cn tn ti sau khi SQL Server shutdown

Remote: gii hn vic thc hin mt stored procedure trn remote SQL Server

Extended (xp_) c implement bi cc ngn ng khc v c gi l cc DLL. Sau khi vit xong extended stored procedure, sysadmin ng k extended stored procedure vi SQL Server v sau gn quyn cho users khc thc hin. Extended stored procedures ch c c trong master database.

X l Stored procedure (1)_Initial

Delayed Name Resolution: cho php stored procedure tham chiu n cc i tng cha tn ti trong lc procedure c to. Delayed Name resolution c thc hin trong lc procedure c thc hin

Creation: Cc lnh trong procedure s c phn tch c php theo c php ca T-SQL. Nu thnh cng, tn ca stored procedure c lu trong SysObjects table, cn text ca procedure lu trong SysComments.

Execution: Khi ln th nht m procedure c thc hin hoc khi procedure phi recompile, query processor s c procedure trong process c gi l resolution.

Sau giai on resolution, SQL Server s to ra mt s thc hin v t s ny trong procedure cache

X l stored procedure (2)_ Subsequent

Li ch ca stored procedure

Cho php lp trnh theo hng modular (modular programming)

Thc thi nhanh hn, gim c vic chim dng ng truyn mng

Bo mt.

X l cc chc nng v chia s vi cc ng dng khc

C php to procedure

CREATE PROCEDURE procedure_name [ { @parameter data_type } [ VARYING ] [ = default ] [ OUTPUT ] ] [ ,...n ]

[ WITH { RECOMPILE | ENCRYPTION | RECOMPILE ,

ENCRYPTION } ] AS

sql_statement [ ...n ]

procedure_name: tn stored procedure

@parameter: tham s, c ti a 2.100 parameters trong mt rpocedure data_type : kiu d liu ca

tham s, bao gm tt c kiu d liu trong SQL Server.

VARYING: ch nh kt qu ca tham s tr v l mt result set. Ch c p dng cho cursor parameters.

default: gi tr mc nhin, nu tham s c gi tr mc nhin th khi thc hin procedure, c th user khng cn truyn tham s vo khi thc thi

OUTPUT : ch nh rng y l output parameter

RECOMILE: procedure s c dch li mi khi thc thi

ENCRYPTION: m ho m lnh ca lnh create procedure khi lu vo table syscomment

V d: CSDL Northwind

To procedure P1 lit k danh sch tt c cc products

Create procedure

To procedure P2 cp nht ga cho cc sn phm tng 10%

Create procedure

Lu

C th tham chiu n cc tables, view, procedure khc cng nh cc temporary table

to mt procedure, user phi c quyn CREATE PROCEDURE (sysadmin, hoc database owner)

Kch thc ca procedure ti a l 128 MB

C th lng 32 cp procedure

Dng procedure sp_helptext hin th ni dung text ca stored procedure m user to

Khng th kt hp lnh create procedure vi cc lnh SQL khc to thnh mt b lnh (batch)

Ch c th to procedure trong database hin hnh.

Thc thi procedure

Lnh thc thi mt stored procedure:

EXECUTE

[ @return_status = ] procedure_name

[ [ @parameter = ] { value | @variable

[ OUTPUT ] | [ DEFAULT ] ]

[ ,...n ]

[ WITH RECOMPILE ]

Ch nh rng ly gi tr tr v ca tham s

Ch nh rng ly gi tr default ca tham s

Ch nh rng procedure phi recompile trc khi thc hin

V d Thc thi procedure P1 v P2:

Execute P1

go

Execute P2

go

V d 2:

Create procedure Mexico_Customers

as

select * from customers

where country=Mexico

go

Execute Mexico_customers

Procedure c tham s create proc CustomerListOfCountry

@country varchar(40)

as

select customerid, CompanyName from customers where country=@country

go

execute CustomerListOfCountry Canada

Hoc truyn tham s vi gi tr khc

execute CustomerListOfCountry USA

Nu khng truyn tham s:

Execute CustomerListOfCountry ????????

Procedure c tham s c gi tr default

create proc CustomerList @country varchar(40)='canada'

as

select customerid, CompanyName from customers where country=@country

go

Gi thc thi c : execute CustomerList Mexico

Gi thc thi khng truyn tham s:

Execute CustomerList

Procedure dng output parameter To Procedure tr v s lng khch hng c gi tr country l

tham s truyn vo:

create proc P2

@country varchar(40) = '%', @total integer OUTPUT

AS

SELECT @total = count(*) FROM customers WHERE country like @country

Go

Thc thi procedure P2

declare @sluong integer

Execute P2 'canada', @sluong output

SELECT 'The total customers of canada is ' +str(@sluong,4)

go

Tham s c kiu l cursor

Ch dng cho tham s OUTPUT.

Nu kiu ca tham s l cursor th VARYING v OUTPUT l bt buc.

Nu VARYING c ch nh cho mt tham s th kiu d liu ca tham s phi l cursor v t kho OUTPUT phi c ch nh.

Kiu d liu Cursor (1)

c dng trong procedure hoc trigger

Cha result set column, record

X l cursor: Khai bo bin kiu cursor cha d liu tr v

Kt hp cursor vi cu lnh select bng lnh DECLARE CURSOR

Dng lnh OPEN m cursor

Dng lnh FETCH INTO mt record hin hnh vo cc bin tng ng vi tng column.

Dng lnh CLOSE ng cursor

Kiu d liu Cursor (2)

sp_cursor_list ly ra danh sch cc cursor hin c

sp_describe_cursor, sp_describe_cursor_column v sp_describe_cursor_tables xem c tnh ca cursor

Sau khi cursor m, hm @@CURSOR_ROWS tra v s lng record

Sau lnh FETCH, hm @@FETCH_STATUS phn nh trng thi fetch sau cng (0,-1)

System stored procedure Description

sp_cursor_list Returns a list of cursors currently visible on the connection and their attributes.

sp_describe_cursor Describes the attributes of a cursor, such as whether it is a forward-only or scrolling cursor.

sp_describe_cursor_columns Describes the attributes of the columns in the cursor result set.

sp_describe_cursor_tables Describes the base tables accessed by the cursor.

75

SCROLL: Cursor c th di chuyn hai chiu

Local: Bin c phm vi local

C php khai bo cursor

DECLARE cursor_name CURSOR [ LOCAL | GLOBAL ] [ FORWARD_ONLY | SCROLL ] [ STATIC | KEYSET | DYNAMIC | FAST_FORWARD ] [ READ_ONLY | SCROLL_LOCKS | OPTIMISTIC ] FOR select_statement [ FOR UPDATE [ OF column_name [ ,...n ] ] ]

Cursor_name: tn bin cursor

Global: Bin c phm vi Global, c th truy xut trong bt k procedure hoc b lnh no

FORWARD_ONLY: Cursor ch di chuyn mt chiu t dng u n dng cui

Static: nh ngha mt cursor l static

DYNAMIC: nh ngha mt cursor phn nh tt c cc thay i ca d liu trong result set.

FAST_FORWARD: ch nh FORWARD_ONLY, READ_ONLY cursor. FAST_FORWARD khng th c ch nh vi SCROLL hoc FOR_UPDATE

KEYSET: cc thnh phn v th t cc dng trong cursor c nh khi cursor c m. Tp cc kho trong cursor c lu trong mt table trong database tempdb gi l keyset.

READ_ONLY: khng cho php cp nht thng qua cursor

OPTIMISTIC: SQL Server khng lock cc dng nu nh chng c c vo cursor.

FOR UPDATE [OF column_name [,...n]]: nh ngha cc ct c th cp nht trong cursor.

SCROLL_LOCKS: kho cc d liu m c c vo cursor

V d 1

DECLARE customer_cursor CURSOR

FOR SELECT * FROM customers

OPEN customer_cursor -- m cursor

FETCH NEXT FROM customer_cursor

V d 2 (1)

DECLARE @customerId varchar(11), @CompanyName varchar(30), @message varchar(80)

PRINT "-------- Customer report --------

DECLARE customer_cursor CURSOR

FOR SELECT customerid, companyName FROM customers WHERE country = "USA"

OPEN customer_cursor

FETCH NEXT FROM customer_cursor INTO @customerid, @companyName

V d 2 (2) While @@FETCH_STATUS = 0

begin

print Customer ID: + @customerID

print Company Name: + @companyName

Fecth next from customer_cursor into @customerid, @companyName

end

Close customer_cursor

Deallocate customer_cursor

go

S dng OUTPUT cursor parameter USE northwind

CREATE PROCEDURE customer_cursor @customer_cursor CURSOR VARYING OUTPUT AS

SET @customer_cursor = CURSOR FORWARD_ONLY STATIC

FOR

SELECT * FROM CUSTOMERS

OPEN @customer_cursor

GO

S dng tham s cursor tr v

DECLARE @MyCursor CURSOR

EXEC customer_cursor @customer_cursor = @MyCursor OUTPUT

WHILE (@@FETCH_STATUS = 0)

BEGIN

FETCH NEXT FROM @MyCursor

END

CLOSE @MyCursor

DEALLOCATE @MyCursor

Bi tp ng dng To procedure v thc thi in ra company name

c s lng orders nhiu nht

To proc p1 tr v doanh thu ca nm truyn vo, nu user khng truyn ngy vo th ly nm hin hnh

Khai bo mt procedure CustomersOfCountryCursor ly ra mt cursor cha cc record ca table customers c country bng gi tr truyn vo. Thc thi CustomersOfCountryCursor v in ra cc d liu c trong cursor tr v.

Bi tp p dng (database QLVT)

1. To procedure P1 ly ra danh sch cc ho n gm cc thng tin: MAHD, NGAY, TENKH, TONGTG

2. To procedure P2 xo cc chi tit ho n ca ho n c m l tham s truyn vo

3. To procedure P3 tnh tng doanh thu ca nm vi nm l tham s truyn vo v tr v gi tr l tng doanh thu tnh c.

Tm tt ni dung bui hc

Stored procedure trong SQL Server ging procedure trong cc ngn ng lp trnh

X l nhanh hn batch

Procedure c th c cc tham s input v output

thc thi mt stored procedure dng lnh execute

Q & A

To proc ly ra danh sch khch hang c da ch l tham s truyn vo:

CREATE PROC P2 @DC VARCHAR(50)

AS

select * from khachhang where diachi=@dc

Create proc P1

As

Select hd.mahd, tenkh, ngay, sum(sl*giaban) as tongtg

From hoadon hd, khachhang kh, chitiethoadon cthd

Where (hd.mahd=cthd.mahd) and

(kh.makh = hd.makh)

Group by hd.mahd, tenkh, ngay

Create proc p2 @mahd nvarchar(10)

As

delete * from chitiethoadon where mahd=@mahd

Go

-- thuc thi

Exec p2 hd002

go

Create proc p3 @nam int, @dt int OUTPUT

As

select @dt=sum(sl*giaban)

From chitiethoadon cthd, hoadon hd

Where (hd.mahd=cthd.mahd) AND

year(ngay)= @nam

Go

Declare @dt int

Exec p3 2000,@dt OUTPUT

Print Doanh thu nam 2000 la + str(@dt,8)

Trong QLVT To procedure ly ra tn ca cc khch hng

mua hng trong thng . V nm .. (tham s input). Danh sch ny c tr v trong mt kiu cursor.

Thc thi P4 ly ra danh sch cc khch hng ca thng 6 nm 2000 v in ra tn ca cc khch hng .

Trong NorthWind Khai bo mt procedure CustomersOfCountryCursor

ly ra mt cursor cha cc record ca table customers c country bng gi tr truyn vo. Thc thi CustomersOfCountryCursor v in ra cc d liu c trong cursor tr v.

TRIGGER Sau bi hc ny, sinh vin c th: Hiu c trigger l g, cng dng ca n To trigger Xo trigger Thay i trigger

Ni dung

1. Trigger l g ?

2. Khi no ta cn s dng Trigger

3. c im ca Trigger

4. To Mt Trigger nh th no?

5. Cc v d Trigger

6. Cc lu

Trigger l g ? Trigger l mt stored procedure c bit c gi t ng khi

user cp nht d liu trn mt table

c kt hp vi table: c nh ngha trn mt table c th .

c gi t ng: Khi c mt thao tc cp cht d liu trn table (insert, update, hoc delete) th trigger ca thao tc tng ng c t ng thc hin.

Khc vi procedure, trigger khng th c gi trc tip, khng nhn tham s

L mt phn ca transaction: nhng lnh trong trigger c xem l mt single transaction, c th c roll back t bt k ch no trong trigger

Khi no ta cn s dng trigger Ta ch s dng trigger khi m cc bin php bo m data

intergrity khc nh Constraints khng th tha mn yu cu ca ng dng.

Thc hin cascade updates v cascade deletes qua cc table quan h trong database

p buc tnh ton vn d liu phc tp: Thc hin cc rng buc c tham chiu n cc column trong nhiu table.

nh ngha Custom Error Messages: Dng trigger tr v cc chui thng bo trng thi ca mt hng ng no .

Bo tr cc d liu khng c chun ho:!

c im ca Trigger

Trigger c thc hin t ng sau khi lnh INSERT, UPDATE, hoc DELETE c thc hin trn mt table m trigger c nh ngha. Cn cc constraints v INSTEAD OF trigger s c kim tra trc khi lnh INSERT, UPDATE, hoc DELETE thc hin.

Constraints s c kim tra trc trigger. Mt table c th c nhiu Triggers cho mt action. Mt trigger

c th c nh ngha cho nhiu action.

c im ca Trigger

Khi c nhiu trigger trong mt table, th table owner c th dng procedure h thng sp_settriggerorder ch nh trigger u v trigger cui thc thi. Th t ca cc trigger cn li khng th sp xp c.

User phi c quyn thc hin tt c cc lnh m c nh

ngha trong Triggers Table Owners khng th to ra cc Triggers trn Views hoc

Temporary Tables nhng c th tham chiu n view v temporary.

c im ca Trigger

Triggers khng tr kt qu v.

Triggers c th iu khin multi-row actions: mt hnh ng INSERT, UPDATE, hoc DELETE gi mt trigger c th nh hng ln nhiu dng d liu, Ta c th chn: X l tt c cc dng cng vi nhau trong trng hp cc

dng nh hng phi tho iu kin ca trigger.

X l tng dng tha iu kin.

Logic tables

Khi c action Insert, table logic inserted sinh ra, c cu trc ging vi cu trc table c insert, c d liu l record ang c insert

Khi co action delete, table deleted sinh ra, c cu trc ging vi cu trc table b deleted, c d liu l record ang b xo

Khi c action update, c 2 table inserted v deleted

To trigger CREATE TRIGGER trigger_name

ON { table | view } [ WITH ENCRYPTION ] { {{ FOR | AFTER | INSTEAD OF }

{ [ INSERT ] [ , ] [ UPDATE ] [ , ] [ DELETE] } [ WITH APPEND ]

AS [ { IF UPDATE ( column ) [ { AND | OR } UPDATE ( column ) ] [ ...n ] } ] sql_statement [ ...n ] } }

Tham s (1)

Table | view : tn view/table m trigger c thc hin khi c action tng ng.

WITH ENCRYPTION: m ho nt dung text ca lnh create trigger trong table syscomments.

AFTER: Trigger s c gi ch khi tt c cc hnh ng thc hin xong. Cc kin tra constrain v cascade s c kim tra hon thnh trc khi trigger thc hin. Default l AFTER nu ch c t kho FOR c ch nh. AFTER trigger khng th nh ngha trn view.

INSTEAD OF: ch nh trigger oc thc hin thay cho action ca trigger. INSTEAD OF triggers khng cho php cp nht d liu trn view c WITH CHECK OPTION.

Tham s (2)

{ [DELETE] [,] [INSERT] [,] [UPDATE] } : ch nh action gn vi trigger. i vi INSTEAD OF triggers, action DELETE khng cho php trn table m c relationship m ch nh CASCADE ON DELETE. Tng t, action UPDATE khng cho php trn table c relationships m CASCADE ON UPDATE.

Table deleted v inserted l logical tables. Chng c cu trc ging vi table m trigger c nh ngha, cha cc dng gi tr c hoc mi m c th thay i bi action ca user. Ta c truy xut d liu trong 2 table ny trong nh ngha trigger.

Tham s (3)

Cc gi tr kiu text, ntext, hoc image trong table inserted v deleted khng truy xut c.

Khi trigger mc 65, gi tr null s c tr v ct c kiu text, ntext, hoc image trong table inserted hoc deleted nu ct cho php null; chui zero-length c tr v nu ct c th null.

IF UPDATE (column): kim tra action update trn ct c ch nh, khgn dng cho action delete.

With Append: Chn thm trigger ny vo cc trigger c trc

V d

Use Northwind GO CREATE TRIGGER Empl_Delete ON Employees FOR DELETE AS IF (SELECT COUNT(*) FROM Deleted) > 1 BEGIN RAISERROR( 'You cannot delete more than one employee at a time.', 16, 1) ROLLBACK TRANSACTION END

Nhng lnh sau y khng c dng trong nh ngha trigger

V d (1) USE pubs IF EXISTS (SELECT name FROM sysobjects WHERE name =

'reminder' AND type = 'TR') DROP TRIGGER reminder GO CREATE TRIGGER reminder ON titles FOR INSERT, UPDATE AS RAISERROR (50009, 16, 10) GO

Alter trigger ALTER TRIGGER trigger_name ON table [WITH ENCRYPTION] {{FOR {[,] [DELETE] [,] [UPDATE] [,][INSERT]} AS sql_statement [...n] } | {FOR {[,] [INSERT] [,] [UPDATE]} AS IF UPDATE (column) [{AND | OR} UPDATE (column) [,...n]] sql_statement [...n] } }

Xo trigger DROP TRIGGER trigger_name

Bi tp p dng (QLVT) To trigger khi insert mt record vo trong table

CHITIETHOADON, th cp nht li SLTON ca vt t trong table VATTU

To trigger khng cho php mt ho n c nhiu hn 4 chi tit ho n

To trigger khng cho php hai vt t trng tn

To trigger khng cho php xo cng lc nhiu hn mt khch hng

To trigger khng cho php xo mt vt t m c t nht mt chi tit ho n ca vt t .

To trigger kim tra s lng bn ra ca mt vt t phi nh hn s lng tn trong kho

create trigger t1

on chitiethoadon1

for insert

as

declare @sl int, @mavt varchar(10)

select @sl = sl, @mavt = mavt from inserted

update vattu1 set slt=slt- @sl where mavt =@mavt