Interested to Buy Any Domain ? << Click Here >> for more details...
can foreign key take role of primary key?
- 5 Answers
- 9724 Views
- CarrizalSoft Technologies, TCS, Villa Marie, I also Faced
- E-Mail Answers
Answer Posted / gaurav
Yes. This situation occurs in one-to-one relationships.
For example:
create table Table1
( T1_Id integer not null primary key
, T1_Data varchar(9) not null
)
create table Table2
( T2_Id integer not null primary key
, T2_Data varchar(37) not null
, foreign key (T2_Id) references Table1 (T1_Id)
)
Why would someone design two tables like this? If it's a
one-to-one relationship, couldn't you just include T2_Data
in Table1? Yes, you could, although then you would also need
to allow T2_Data to be NULL, if not every T1_Id has a
matching T2_Id—in this case it's actually a
one-to-zero-or-one relationship.
If it's a true one-to-one relationship, where every T1_Id
has a matching T2_Id, then you could combine them without
NULLs. Then the only reason why you might want separate
tables would be if T2_Data were (a) infrequently queried,
and (b) so large that it would result in many fewer physical
rows on a physical database page, which would imply poorer
performance for queries that used only T1_Data.
| Is This Answer Correct ? | 10 Yes | 0 No |
Post New Answer View All Answers
What are the security related catalog views? : sql server security
Explain triggers in sql?
What is the return type of executeupdate ()?
How many instances per computer are there in sql server 2000?
What are the benefits of normalization?
How to list all dsn entries on your local machine using odbc_data_source()?
How to encrypt Strored Procedure in SQL SERVER?
What is an identity?
What are “lock” hints?
What are the diifferences between the ms sql server vs mysql?
What is system stored procedures?
Are connections to sql server encrypted?
Explain about system stored procedure?
What are the dmvs?
Explain what are partitioned views and distributed partitioned views?
