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Updating a row in a table with a composite primary key composed of 3 primary keys and one foreign key

Posted on 2007-11-19
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Last Modified: 2008-09-08
I have a table with a composite primary key composed of the fields  a,b and c and a foreign key 'd' and several other columns.
I hava a grid view for which I have dropdowns fora,b,c and d columns.
Now, my question is, when I update a row, can I update a, b, c or d individually while updating a row?

Please let me KNOW asap.
It's extremely urgent.

Thanks in advance.


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Question by:amukta
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Expert Comment

by:Guy Hengel [angelIII / a3]
ID: 20317794
>Now, my question is, when I update a row, can I update a, b, c or d individually while updating a row?
yes, that is possible.
however, you should rethink your table design, and add a dedicated column as primary key (and eventually make your current pk a unique key).
this will make things, related to this table, a lot easier.

having composite primary keys is rarely a good design, with "1 exception":
a relation table with just the 2 foreign key field could very well be implemented with the primary key on just that 2 fields...
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Accepted Solution

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imitchie earned 500 total points
ID: 20317861
yes you can still update parts of composite primary keys individually. however, if it's referenced as a foreign key from another table, then it may be blocked due to constraints.

create table tab (a int, b int, c int, d int, primary key(a,b,c))
insert into tab (1,2,3,4)

these are all legal:
update tab set b = 7 where a = 1
update tab set c = 8 where a = 1
update tab set d = 9, b = b + 1where a = 1
update tab set a = 2 where a = 1
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Author Comment

by:amukta
ID: 20319733
IMITCHIE,

THANK YOU!
I HAVE ONE MORE QUESTION.
IS IT FINE TO UPDATE THIS WAY?
UPDATE TAB SET C=8 WHERE A=1,B=2,C=3 AND D=4?
similarly update tab set b=3 where A=1,B=2,C=3 AND D=4?
update tab set c=4 where A=1,B=2,C=3 AND D=4?
AND SINCE D IS THE FOREIGN KEY, CAN I UPDATE IT SAYING
UPDATE TAB SET D=9 WHERE A=@A, B=@B, C=@C AND D=@D?

PLEASE LET ME know ASAP.
THANKS IN ADVANCE
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Author Comment

by:amukta
ID: 20319760
ONE MORE QUESTION AND CN I ALSO UPDATE LIKE THIS?
UPDATE A=@A, B=@B,C=@C,D=@D WHERE A=@A,B=@B,C=@C,D=@D?
NOPE RIGHT? OR CAN I DO SO?

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Author Comment

by:amukta
ID: 20319767
ONE MORE QUESTION AND CN I ALSO UPDATE LIKE THIS?
UPDATE A=@A, B=@B,C=@C,D=@D WHERE A=@A,B=@B,C=@C,D=@D?
NO RIGHT? OR CAN I DO SO?
0
 

Author Comment

by:amukta
ID: 20319774
ONE MORE QUESTION AND CN I ALSO UPDATE LIKE THIS?
UPDATE A=@A, B=@B,C=@C,D=@D WHERE A=@A,B=@B,C=@C,D=@D?
NO RIGHT? OR CAN I DO SO?
0

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