Questions tagged [dependencies]
88 questions
9
votes
4 answers
What exactly is overlapping candidate key?
Can some one please explain to me in simple terms what is overlapping candidate key ? What is overlapping as the name suggests?
Consider the below relation
R(L,M,N,O,P)
{
M -> O
NO -> P
P -> L
L -> MN
}
Which of the above…
vikkyhacks
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8
votes
1 answer
Functional dependencies applies to whole database or to a particular relation?
I am new to dbms. I saw a lecture video about functional dependencies. But I am confused a bit that whether functional dependency is a constraint put on whole database or on a particular schema?
Saravanan
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7
votes
1 answer
How to safely replace the old table with its cleaned copy?
I have created a table_cleaned like table and inserted unique values from table into table_cleaned. Now I want to replace table with table_cleaned with
DROP TABLE table;
ALTER TABLE table_cleaned rename to table;
but the first statement gives…
Dmitriy Grankin
- 259
- 4
- 12
5
votes
1 answer
Drop partition scheme with orphan indexes
I have a partition scheme in my SQL Server database that I am trying to drop. This scheme was used by 2 indexes, which I deleted.
I can't delete the scheme, since it appears to still be used by the indexes, even though they don't exist…
Shahar Mosek
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5
votes
1 answer
What permissions are needed to view dependencies?
My company is moving to a much more restrictive security model in the near future.
As part of that we are changing specific servers to the new model and testing all our existing processes. One of the processes that I use a lot utilizes the SMO…
JNK
- 18,064
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5
votes
1 answer
Why a dropped index is still there, and does it prevent a table from being altered?
I have a column (named RequestDate) which I need to change from NULL to NOT NULL, but there's a clustered index on that column, so I first need to drop that index.
Originally, the index was created using:
CREATE CLUSTERED INDEX IX_RequestDate
…
HeyJude
- 467
- 7
- 18
5
votes
1 answer
Attempting to identify minimal functional dependencies in a Compact Disc details scenario
I believe this relation/table is in first normal form (1NF):
Collection (cd_id, title, label, artist, type, country, song_id, song_title, length)
Note: Bold means keys.
What I have managed to identify:
{cd_id, song_id} → {song_title, length}
{cd_id}…
Erik Eriksson
- 171
- 8
5
votes
1 answer
Get list of functions used in a view
Say I have a Function like this:
create function house_analysis(ingeo geometry)
returns table(count_all numeric, count_important numeric) as
$$
select count(*), count(*) filter (where h.import_flag)
from house_table h where…
thomjah
- 115
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4
votes
1 answer
Identifying functional dependencies
I'm having trouble understanding the logic in use for identifying functional dependancies.
Looking at the sample relation below, I understand fd1 - fd3. But when I look at fd4 and fd5, its logic makes me believe that fd6 and fd7 would also be…
JazzMaster
- 141
- 2
4
votes
1 answer
Way to obtain full list of column dependencies for stored procedure?
I've built a stored procedure (which we can call sproc_deps) that uses sys.sql_expression_dependencies and sys.dm_sql_referenced_entities. I want it to list out all of the tables and columns used by a stored procedure of the user's choice. This…
Antidiscrete
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4
votes
0 answers
Can the Chase test algorithm only modify attributes on the right side of a functional dependency?
I'm attempting to apply the Chase Algorithm to determine if a decomposition is a lossless join decomposition.
Functional Dependencies = {A → C, B → D, C → D, DE → C, CE → A}
Here is my initial matrix:
Can I apply DE → C to remove the subscript from…
student_1123
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- 3
3
votes
2 answers
Why is this relation in 3NF?
I have a relation:
R4 = {{T,U,V}, {T → U, U → T, T → V}}
I know from looking at the answer key that this relation is in BCNF.
I'm going through the process of rigorously determining what normal form the relationship adheres to. It's clear to me…
Wug
- 133
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3
votes
1 answer
Normalization with two potential primary keys
I have the following STUDENT relation in first normal form, where id has been identified as the primary key (email here is also unique for all tuples):
STUDENT(id, email, first_name, last_name)
I want to normalize this relation/table such that it…
Shnick
- 141
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3
votes
1 answer
Questions Concerning the Chase Test
[5 Marks] Let R(A,B,C,D,E) be decomposed into relations with the following three set of attributes {A,B,C}, {B,C,D}, and {A,C,E}. For each of the following sets of FD's, use the chase test to tell whether the decomposition of R is lossless. For…
Niroosh Ka
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3
votes
2 answers
Is the inverse of Armstrong's Axioms valid as well?
I have been looking into Armstrong's axioms a little bit. In a homework[1] exercise I was asked to prove A→G is in F-closure. I managed to get it at this point:
AB → GB
Being at this point, can I simply say that A → G as it seems pretty…
johndoe123
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