sql 07 trigger

7/31/2019 SQL 07 Trigger

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TRIGGERTRIGGER


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2

Ni dung chi tit

Gii thiu To Trigger

Hiu chnh Trigger

Xa Trigger V d


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Gii thiu

TRIGGER l mt Stored procedure c bit tng c chy mi khi c mt hnh ngno xy ra c lin quan n n.

Cc hot ng xy ra gip TRIGGER hotng: Insert, Delete, Update (DML).TRIGGER khng c thc thi mt cchtng minh nn cn thn trng khi dng

TRIGGER.


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Gii thiu

TRIGGER hot ng gn ging cc hm bts kin trong javascript. N ch c kchhot khi xy ra mt hnh ng m c th l

cc thao tc Insert, Delete, Update. N hot ng mt cc th ng nn chng ta

khng th bit trigger thc thi khi no.


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S dng trigger lm g?

m bo tnh rng buc ton vn cho CSDL. Kim sot d liu hin c trong CSDL khi c

thay i gi tr ca mt mu tin trong bng.

Kim tra d liu mi nhp vo c tha mn iukin khng.

Kim chng khi xa mu tin trong bng.

T ng cp nht d liu cho bng B khi d liu

bng A thay i (khi 2 bng c quan h vinhau).


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6

Triggers hot ng nh th no?

Triggers c thc hin t ng sau khi lnhINSERT, UPDATE, hoc DELETE c thc hintrn mt table m trigger c nh ngha. Cncc constraints v INSTEAD OF trigger s c

kim tra trc khi lnh INSERT, UPDATE, hocDELETE 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. Th t thi hnh s l: trigger INSTEAD OF, cc

constraint, v sau cng l trigger AFTER.


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7

Triggers hot ng nh th no?

Khi c nhiu trigger trong mt table, th table ownerc 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 thamchiu n view v temporary.


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Triggers hot ng nh th no

Triggers khng tr kt qu v. Triggers c th iu khin multi-row actions: mt

hnh ng INSERT, UPDATE, hoc DELETE gimt trigger c th nh hng ln nhiu dng dliu, Ta c th chn:- X l tt c cc dng cng vi nhau trong trng

hp cc dng nh hng phi tha iu kin catrigger.

- X l tng dng tha iu kin.


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Insert TRIGGER

c thc hin mi khi mu tin mi c chnvo bng

Mt bng tm Inserted s c sinh ra chamu tin cn chn


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Delete TRIGGER

c thc hin mi khi cc mu tin trong bngb xa.

Mt bng tm Deleted c sinh ra lu ccmu tin b xa.


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Update TRIGGER

c thc hin khi cc bn cc mu tin cabng c cp nht

Hai bng Inserted v Deleted s c sinh ra. Bng Inserted s lu thng tin cc mu tin mi

c sa, bng Deleted s lu thng tin ccmu tin c.


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Instead of TRIGGER

Trigger cho php cp nht d liu cc bngthng qua view c lin kt nhiu bng

Hoc by trc khi cc constraint c tcdng.


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Mt s ch :

Mt bng c nhiu trigger

Mi mt trigger c tn duy nht

Trong trigger thng dng mnh IFEXISTS

S dng trigger trong ton vn d liu

S dng trigger trong rng buc tham chiu.


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Ni dung chi tit

Gii thiu To Trigger

Hiu chnh Trigger

Xa Trigger

V d


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To Trigger

C php

- : tn Trigger

- : tn bng cn nh ngha Trigger

- INSERT, UPDATE, DELETE: nh ngha thao tc kchhot Trigger

CREATE TRIGGER ON

FOR< [INSERT] [,] [UPDATE] [,] [DELETE]>

AS


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To Trigger (tt)

V d: rng buc lng nhn vin phi l s dng

CREATE TRIGGERLUONG_DUONG ON NHANVIEN

FOR INSERT, UPDATE

AS

BEGINIF (SELECT COUNT(*) FROM INSERTED WHERE LUONG < 0) > 0

BEGIN

Print N'Lng phi l s dng'

Rollback Tran

ENDEND


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17

Ni dung chi tit

Gii thiu To Trigger

Hiu chnh Trigger

Xa Trigger

V d


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Hiu chnh Trigger

C phpALTER TRIGGER ON

FOR

AS


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Hiu chnh Trigger (tt)

V d: rng buc 0 0

BEGIN

Print0


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Ni dung chi tit

Gii thiu To Trigger

Hiu chnh Trigger

Xa Trigger

V d


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Xa Trigger

C php

V d

DROP TRIGGER

DROP TRIGGERLUONG_DUONG


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Ni dung chi tit

Gii thiu To Trigger

Hiu chnh Trigger

Xa Trigger

V d


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V d 1

Rng buc lng nhn vin phi tng

CREATE TRIGGERLUONG_TANG ON NHANVIEN

FOR UPDATE

AS

IF UPDATE(LUONG)BEGIN

IF (SELECT COUNT(*) FROM INSERTED I, DELETED D

WHERE D.LUONG >= I.LUONGAND I.MANV=D.MANV) > 0

BEGIN

Print N'Lng nhn vin phi tng'

Rollback Tran

END

END


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V d 2

Rng buc nhn vin phi t 18 tui tr ln

CREATE TRIGGERTUOI_18_TROLEN ON NHANVIEN

FOR INSERT, UPDATE

AS

IF EXISTS (SELECT * FROM INSERTED I

WHERE DATEADD(YY,18,NGSINH) > GETDATE())

BEGIN

Print N'Nhn vin phi 18 tui tr ln'

Rollback Tran

END


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V d 3

Rng buc khng cho php thm, sa bngNHANVIEN nu PHG khng c trong bngPHONGBAN

CREATE TRIGGERTONTAI_PHONG ON NHANVIEN

FOR INSERT, UPDATE

AS

IF NOT EXISTS (SELECT * FROM INSERTED , PHONGBAN

WHERE PHG = MAPHG)

BEGINPrint NM phng cha tn ti

Rollback Tran

END


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V d 4

Rng buc khng cho sa MAPHG trong bngPHONGBAN

CREATE TRIGGERKHONG_SUA_KHOACHINH ON PHONGBAN

FOR UPDATE

ASIF UPDATE(MAPHG)

BEGIN

Print NKhng c sa kha chnh

Rollback Tran

END


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V d 5

Sa MAPHG trong bng PHONGBAN th phi salun nhng mu tin c lin quan trong bngNHANVIEN

CREATE TRIGGERSUA_DAYCHUYEN ON PHONGBAN

FOR UPDATEAS

IF UPDATE(MAPHG)

BEGIN

UPDATE NHANVIEN

SET PHG = I.MAPHGFROM NHANVIEN, DELETED D, INSERTED I

WHERE PHG = D.MAPHG

END


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V d 6

Khng cho xa NHANVIEN nu nhn vin ctrong bng PHANCONG

CREATE TRIGGERKHONG_XOA_NV_CO_PHANCONG ON NHANVIEN

FOR DELETE

AS

IF (SELECT COUNT(*) FROM DELETED , PHANCONG

WHERE MANV = MA_NVIEN) > 0

BEGIN

Print NNhn vin c trong phn cng

Rollback Tran

END

sql 07 trigger

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