??1sql?server?2000?觸發器,表同步更新的問題?
??2有三個表，A?，B，C
??3A、B表中含有:?A1,B1,C1?三個字段,
??4C?表中存放A、B表中的A1、B1、C1?的集合,
??5字段類型都為nvarchar(10),
??6當表A的數據被更新、刪除、插入后要反映到C表。
??7當表B的數據被更新、刪除、插入后要反映到C表。
??8假定A,B表中在a1,b1,c1上有唯一索引
??9
?10
?11??????這個問題如果純屬從理論來說，是很容易解決的，因為從要求可知，實質上C表存放的數據即為A、B表的并集。可以在A、B表上創建相同的trigger，一旦A、B表上有變化，比如插入、刪除或更新時，即清空C表數據，然后把A、B表的數據union后插入C表中即可實現目的:)呵呵呵。。。
?12
?13??????下面的trigger的實現原理是：
?14
?15???????當A表插入數據時，檢查C表中是否有A表將要插入的數據，如果無，則將這行數據插入到C表中，反之，則不需要操作。
?16
?17???????當A表update時,?檢查B表中是否有更新前這行數據，如果有，則C表中應該保留這行數據且把A表中更新后的數據也插入到C表中去。如果B表中沒有A表更新前的這行數據且C表中沒有A表更新后的這行數據，則需要用A表更新后的數據來更新C表中與A表更新前這行數據相同的數據；如果B表中沒有A表更新的的這行數據且C表中有A表更新后的這行數據，則需要從C表中刪除跟A表更新前相同的那行數據（因為更新A表后，A表和B表都沒有A表更新前的那行數據了，則這行數據顯然在C表中不應該再存在了）。
?18
?19???????當A表中刪除時，檢查B表是否還存在A表要刪除的這行數據，如果有，則不能刪除C表中與A表要刪除的數據相同的行。反之，則執行刪除操作。
?20
?21
?22????B表中的trigger跟A表中的原理相同。
?23
?24
?25CREATE?TRIGGER?SYNC_C_BY_A
?26ON?A
?27AFTER?INSERT,UPDATE,DELETE
?28AS
?29Declare?@Dml????????????TinyInt??--1:Insert?2:Update?3:Delete????????????
?30Declare?@RowsD??????????Int????????????
?31Declare?@RowsI??????????Int?
?32Declare?@A1_D???????????nvarchar(10)
?33Declare?@B1_D???????????Nvarchar(10)
?34Declare?@C1_D???????????Nvarchar(10)
?35--確定是哪一種dml操作????????????
?36Select?@RowsD=Count(*)?From?Deleted????????????
?37Select?@RowsI=Count(*)?From?Inserted????????
?38If?@RowsD=0?And?@RowsI=0????????
?39????Goto?Exit_?????????
?40If?@RowsD=0?And?@RowsI>0????????????
?41????Set?@Dml=1????????????
?42Else????????????
?43???If?@RowsD>0?And?@RowsI>0????????????
?44???????Set?@Dml=2????????????
?45???Else????????????
?46???????If?@RowsD>0?And?@RowsI=0????????????
?47???????????Set?@Dml=3?
?48IF?@DML=1
?49???BEGIN
?50???????--檢查c表中是否已經有A表中新插入的數據行,如果沒有,則也插入
?51???????IF?NOT?EXISTS(SELECT?TOP?1?1?FROM?c,inserted?i?where??c.a1=i.a1?and?c.b1=i.b1?and?c.c1=i.c1)
?52??????????insert?into?c?select?*?from?inserted
?53???END
?54IF?@DML=2
?55???BEGIN
?56???????--檢查B表中是否有A表中更新前的這行數據,如果有,則不需要更新C表中的數據,而是要把A表中更新后的這行數據插入到C表中
?57???????IF?NOT?EXISTS(SELECT?TOP?1?1?FROM?B,DELETED?d?where?b.a1=d.a1?and?b.b1=d.b1?and?b.c1=d.c1)
?58?????????BEGIN????????????
?59?????????????--如果C表中不存在A表更新后的這行數據,則更新C表中跟A表更新前那行數據相同的數據
?60?????????????IF?NOT?EXISTS(SELECT?TOP?1?1?FROM?C,INSERTED?I?WHERE?C.A1=I.A1?AND?C.B1=I.B1?AND?C.C1=I.C1)
?61?????????????????BEGIN
?62?????????????????????UPDATE?C?SET?A1=I.A1,B1=I.B1,C1=I.C1?FROM?C,INSERTED?I,DELETED?D?WHERE?C.A1=D.A1?AND?C.B1=D.B1?AND?C.C1=D.C1
?63?????????????????END
?64?????????????--如果C表中存在A表更新后的這行數據,則需要刪除C表中跟A表更新前相同的那行數據
?65?????????????ELSE
?66?????????????????BEGIN
?67?????????????????????SELECT?@A1_D=A1,@B1_D=B1,@C1_D=C1?FROM?DELETED
?68?????????????????????DELETE?FROM?C?WHERE?@A1_D=A1?AND?@B1_D=B1?AND?@C1_D=C1
?69?????????????????END
?70?????????END
?71???????ELSE
?72??????????insert?into?c?select?*?from?inserted?i?where?not?exists(select?1?from?c?where?i.a1=c.a1?and?i.b1=c.b1?and?i.c1=c.c1)??????
?73???END
?74IF?@DML=3
?75???BEGIN
?76???????--如果B表中不存在A表要刪除的這行數據,則需要從C表中刪除這行數據
?77???????IF?not?exists(select?top?1?1?from?b,deleted?d??where?b.a1=d.a1?and?b.b1=d.b1?and?b.c1=d.c1)
?78???????DELETE?FROM?C?WHERE?EXISTS(SELECT?1?FROM??deleted?d?where??c.a1=d.a1?and?c.b1=d.b1?and?c.c1=d.c1)
?79???END
?80EXIT_:??
?81
?82CREATE?TRIGGER?SYNC_C_BY_B?
?83ON?B
?84AFTER?INSERT,UPDATE,DELETE
?85AS
?86Declare?@Dml????????????TinyInt??--1:Insert?2:Update?3:Delete????????????
?87Declare?@RowsD??????????Int????????????
?88Declare?@RowsI??????????Int?
?89Declare?@A1_D???????????nvarchar(10)
?90Declare?@B1_D???????????Nvarchar(10)
?91Declare?@C1_D???????????Nvarchar(10)
?92--確定是哪一種dml操作????????????
?93Select?@RowsD=Count(*)?From?Deleted????????????
?94Select?@RowsI=Count(*)?From?Inserted????????
?95If?@RowsD=0?And?@RowsI=0????????
?96????Goto?Exit_?????????
?97If?@RowsD=0?And?@RowsI>0????????????
?98????Set?@Dml=1????????????
?99Else????????????
100???If?@RowsD>0?And?@RowsI>0????????????
101???????Set?@Dml=2????????????
102???Else????????????
103???????If?@RowsD>0?And?@RowsI=0????????????
104???????????Set?@Dml=3?
105IF?@DML=1
106???BEGIN
107???????--檢查c表中是否已經有B表中新插入的數據行,如果沒有,則也插入
108???????IF?NOT?EXISTS(SELECT?TOP?1?1?FROM?c,inserted?i?where??c.a1=i.a1?and?c.b1=i.b1?and?c.c1=i.c1)
109??????????insert?into?c?select?*?from?inserted
110???END
111IF?@DML=2
112???BEGIN
113???????--檢查B表中是否有A表中更新前的這行數據,如果有,則不需要更新C表中的數據,而是要把A表中更新后的這行數據插入到C表中
114???????IF?NOT?EXISTS(SELECT?TOP?1?1?FROM?A,DELETED?d?where?a.a1=d.a1?and?a.b1=d.b1?and?a.c1=d.c1)
115?????????BEGIN???????????
116?????????????--如果C表中不存在B表更新后的這行數據,則更新C表中跟b表更新前那行數據相同的數據
117????????????IF?NOT?EXISTS(SELECT?TOP?1?1?FROM?C,INSERTED?I?WHERE?C.A1=I.A1?AND?C.B1=I.B1?AND?C.C1=I.C1)
118????????????????BEGIN
119????????????????????UPDATE?C?SET?A1=I.A1,B1=I.B1,C1=I.C1?FROM?C,INSERTED?I,DELETED?D?WHERE?C.A1=D.A1?AND?C.B1=D.B1?AND?C.C1=D.C1
120????????????????END
121?????????????--如果C表中存在更新B表后的這行數據,則需要刪除C表中跟B表更新前相同的那行數據
122????????????ELSE
123????????????????BEGIN
124????????????????????SELECT?@A1_D=A1,@B1_D=B1,@C1_D=C1?FROM?DELETED
125????????????????????DELETE?FROM?C?WHERE?@A1_D=A1?AND?@B1_D=B1?AND?@C1_D=C1
126????????????????End
127???????????????????
128?????????END
129???????ELSE
130??????????insert?into?c?select?*?from?inserted?i?where?not?exists(select?1?from?c?where?i.a1=c.a1?and?i.b1=c.b1?and?i.c1=c.c1)??????
131???END
132IF?@DML=3
133???BEGIN
134???????--如果A表中不存在B表要刪除的這行數據,則需要從C表中刪除這行數據
135???????if?not?exists(select?top?1?1?from?a,deleted?d??where?a.a1=d.a1?and?a.b1=d.b1?and?a.c1=d.c1)
136???????DELETE?FROM?C?WHERE?EXISTS(SELECT?1?FROM??deleted?d?where??c.a1=d.a1?and?c.b1=d.b1?and?c.c1=d.c1)
137???END
138EXIT_:?

轉載于:https://www.cnblogs.com/Dicky/archive/2005/05/21/160037.html

總結

以上是生活随笔為你收集整理的表同步更新的问题的触发器的全部內容，希望文章能夠幫你解決所遇到的問題。

如果覺得生活随笔網站內容還不錯，歡迎將生活随笔推薦給好友。