Overview on RDBMS
Introduction:
RDBMS is a term used to depict an entire suite of programs for both managing a relational database together with communicating with that relational database engine. Sometimes Software Development Kit (SDK) front-end tools together with consummate administration kits are included with relational database packages (eg: MS Access) In other words, an RDBMS is both the database engine together with whatever other tools that come upward with it.
What is RDBMS?
RDBMS stands for Relational Database Management System. RDBMS information is structured inwards database tables, fields together with records. Each RDBMS tabular array consists of database tabular array rows. Each database tabular array row consists of 1 or to a greater extent than database tabular array fields.
RDBMS shop the information into collection of tables, which mightiness move related yesteryear mutual fields (database tabular array columns). RDBMS also render relational operators to manipulate the information stored into the database tables. Most RDBMS usage SQL equally database inquiry language.
RDBMS CONCEPTS:
What is database?
A database is a logically coherent collection of information with merely about inherent meaning, representing merely about facial expression of existent basis together with which is designed, built together with populated with information for a specific purpose.
What is DBMS?
It is a collection of programs that enables user to create together with hold a database. In other words it is general-purpose software that provides the users with the processes of defining, constructing together with manipulating the database for diverse applications.
What is a Database system?
The database together with DBMS software together is called equally Database system.
Disadvantage inwards File Processing System
Data redundancy & inconsistency.
Difficult inwards accessing data.
Data isolation.
Data integrity.
Concurrent access is non possible.
Security Problems.
Describe the 3 levels of information abstraction
The are 3 levels of abstraction:
Physical level: The lowest degree of abstraction describes how information are stored.
Logical level: The side yesteryear side higher degree of abstraction, describes what information are stored inwards database together with what human relationship with those data.
View level: The highest degree of abstraction describes only constituent of entire database.
What is System R? What are its 2 major subsystems?
System R was designed together with developed over a menstruum of 1974-79 at IBM San Jose Research Center. It is a epitome together with its purpose was to demonstrate that it is possible to build a Relational System that tin move used inwards a existent life surroundings to solve existent life problems, with performance at to the lowest degree comparable to that of existing system.
Its 2 subsystems are
Research Storage
System Relational Data System.
How is the information construction of System R dissimilar from the relational structure
Unlike Relational systems inwards System R
Domains are non supported
Enforcement of candidate key uniqueness is optional
Enforcement of entity integrity is optional
Referential integrity is non enforced
What is Data Independence
Data independence agency that 'the application is independent of the storage construction together with access strategy of data'. In other words, The powerfulness to modify the schema Definition inwards 1 degree should non impact the schema Definition inwards the side yesteryear side higher level.
Two types of Data Independence:
Physical Data Independence: Modification inwards physical degree should non impact the logical level.
Logical Data Independence: Modification inwards logical degree should impact the sentiment level.
NOTE: Logical Data Independence is to a greater extent than hard to achieve
What is a view?How it is related to information independence
A sentiment may move idea of equally a virtual table, that is, a tabular array that does non actually be inwards its ain correct but is instead derived from 1 or to a greater extent than underlying base of operations table. In other words, at that spot is no stored file that straight represents the sentiment instead a Definition of sentiment is stored inwards information dictionary. Growth together with restructuring of base of operations tables is non reflected inwards views. Thus the sentiment tin insulate users from the effects of restructuring together with increment inwards the database. Hence accounts for logical information independence.
What is Data Model?
A collection of conceptual tools for describing data, information relationships information semantics together with constraints.
What is E-R model
This information model is based on existent basis that consists of basic objects called entities together with of human relationship with these objects. Entities are described inwards a database yesteryear a laid upward of attributes
The Entity-Relationship information model is based on a perception of the existent basis which consists of basic objects called entities together with relationships with theseobjects.
Key:
Influenza A virus subtype H5N1 key is an attribute or laid upward of attributes of an entitywhich tin move used to seat it.
Super Keyis a laid upward of 1 or to a greater extent than attributes which, takencollectively, allows an entity to be uniquelyidentified inwards an entity set
Candidate Keyis a super key for which no proper subset is a superkey (i.e., a minimal super key)
Primary Keyis a candidate key chosen yesteryear the database designeras the regulation agency of identifying entities withinan entity set.
ER Model: Constraints
Constraints:
Key Constraints: These are constraints implied yesteryear the beingness of candidate keys. The tabular array Definition includes aspecification implying uniqueness of the attributesconstituting the primary key or alternate keys.
Influenza A virus subtype H5N1 primary key constraint also implies a no-nulls constraint.Referential Constraints:Constraints implied yesteryear the beingness of unusual keys inthe tabular array definition.Other Constraints:Constraints enforcing checks of delineate of piece of job organisation logic of theapplication inwards the tabular array definition.
Features of RDBMS
Relational database administration organisation has diverse next features:-
1-It tin solve whatever complex queries.
2-RDBMS is really secure.A fully RDBMS tin forestall from whatever unauthorized access.
Advantages of RDBMS over DBMS:
• Reliability is improved because the information is non spread across the network together with several applications. Only 1 procedure handles the data.
• Network traffic is greatly reduced. Let’s tell inwards desktop database model – entire database along with indexes is to move sent to client. Where equally inwards Client/server database model only outcome is to move sent to client.
• Upgrading a heavily used desktop database to a well-designed client/server database volition cut database-related network traffic yesteryear to a greater extent than than 95%.
• Performance is improved equally database operations are handled over server, therefore customer PCs volition receive got less processing requirement.
• Security is improved equally information are kept inside a unmarried server. Hacking into a information file that is protected inside the server is much to a greater extent than hard than hacking into a information file on desktop database model.
• Data integrity constraints together with delineate of piece of job organisation rules tin move enforced at server level. You tin specify rules such equally “Marks of whatever plain of report tin non hap 100 inwards whatever subject”
• Data Sharing: SQL is used to coordinate information sharing yesteryear concurrent users, ensuring that they produce non interfere with 1 another.
• Data tin move integrated using multiple platform i.e. LAN, WAN together with WAN. One tin contain information from INTERNET
CODD Rules:
A relational database administration organisation (RDBMS) is a database administration organisation (DBMS) that is based on the relational model equally introduced yesteryear E. F. Codd. Most pop commercial together with opened upward rootage databases currently inwards usage are based on the relational model.
A curt Definition of an RDBMS may move a DBMS inwards which information is stored inwards the sort out of tables together with the human relationship with the information is also stored inwards the sort out of tables.
E.F. Codd, the famous mathematician has introduced 12 rules for the relational model for databases usually known equally Codd's rules. The rules mainly define what is required for a DBMS for it to move considered relational, i.e., an RDBMS. There is also 1 to a greater extent than dominion i.e. Rule00 which specifies the relational model should usage the relational way to create out the database. The rules together with their description are equally follows:-
Rule 0: Foundation Rule
A relational database administration organisation should move capable of using its relational facilities (exclusively) to create out the database.
Rule 1: Information Rule
All information inwards the database is to move represented inwards 1 together with only 1 way. This is achieved yesteryear values inwards column positions inside rows of tables.
Rule 2: Guaranteed Access Rule
All information must move accessible with no ambiguity, that is, Each together with every datum (atomic value) is guaranteed to move logically accessible yesteryear resorting to a combination of tabular array name, primary key value together with column name.
Rule 3: Systematic handling of zilch values
Null values (distinct from empty grapheme string or a string of blank characters together with distinct from null or whatever other number) are supported inwards the fully relational DBMS for representing missing information inwards a systematic way, independent of information type.
Rule 4: Dynamic On-line Catalog Based on the Relational Model
The database description is represented at the logical degree inwards the same way equally ordinary data, therefore authorized users tin apply the same relational linguistic communication to its interrogation equally they apply to regular data. The authorized users tin access the database construction yesteryear using mutual linguistic communication i.e. SQL.
Rule 5: Comprehensive Data Sublanguage Rule
A relational organisation may back upward several languages together with diverse modes of final use. However, at that spot must move at to the lowest degree 1 linguistic communication whose statements are expressible, per merely about well-defined syntax, equally grapheme strings together with whose powerfulness to back upward all of the next is comprehensible:
a. information definition
b. sentiment definition
c. information manipulation (interactive together with yesteryear program)
d. integrity constraints
e. authorization
f. Transaction boundaries (begin, commit, together with rollback).
Rule 6: View Updating Rule
All views that are theoretically updateable are also updateable yesteryear the system.
Rule 7: High-level Insert, Update, together with Delete
The organisation is able to insert, update together with delete operations fully. It tin also perform the operations on multiple rows simultaneously.
Rule 8: Physical Data Independence
Application programs together with final activities rest logically unimpaired whenever whatever changes are made inwards either storage representation or access methods.
Rule 9: Logical Data Independence
Application programs together with final activities rest logically unimpaired when information preserving changes of whatever form that theoretically permit unimpairment are made to the base of operations tables.
Rule 10: Integrity Independence
Integrity constraints specific to a item relational database must move definable inwards the relational information sublanguage together with storable inwards the catalog, non inwards the application programs.
Rule 11: Distribution Independence
The information manipulation sublanguage of a relational DBMS must enable application programs together with final activities to rest logically unimpaired whether together with whenever information are physically centralized or distributed.
Rule 12: Nonsubversion Rule
If a relational organisation has or supports a low-level (single-record-at-a-time) language, that low-level linguistic communication cannot move used to subvert or bypass the integrity rules or constraints expressed inwards the higher-level (multiple-records-at-a-time) relational language.
Normalization:
• Normalisation is a blueprint techniques that is widely used equally guide inwards designing relational database.
• It is a two-step procedure that puts information into tabular sort out yesteryear removing repeating groups emmet therefore removes duplicated information from relational table.
• Thus Normalisation is the procedure of structuring an unstructured relation into structural 1 with the purpose of removing redundancy together with anomalies.
• Normalisation theory is based on normal forms.A relational tabular array is said to move item normal forms if it satisfy a for certain laid upward of constraints.
Functional Dependency : It depict the human relationship betwixt 2 attributes of same relational database tables.One of the attributes is called determinant together with other attribute is called determined.
For eg.- For each value of determinant at that spot is associated 1 together with only 1 value of determined.
Influenza A virus subtype H5N1 -> B
The Influenza A virus subtype H5N1 is determinant together with B is determined therefore nosotros tell that Influenza A virus subtype H5N1 functionally determines B or Bis functionally dependent on A.
Fully Functional Dependence : It states that if Influenza A virus subtype H5N1 together with B are 2 attributes of a relation therefore B is Fully Functionaly Dependent on Influenza A virus subtype H5N1 if B is Functional Dependent on Influenza A virus subtype H5N1 together with non a proper subset of A.
Transitive Dependency : If Bis functional Dependent on Influenza A virus subtype H5N1 together with C is functional dependent on B therefore C is transitive dependent on A.
The next are the types of normal forms:
First Normal Form (1NF)
When a tabular array is broken upward (decomposed)into to a greater extent than tables with all repeating groups(records) of information eliminated, tabular array information is said to move inwards the commencement normal sort out (1NF).
A tabular array is said to move inwards 1st Normal sort out if:
(a) There is no repeating group.
(b) All the key attributes are defined.
(c) All the non-key attributes are dependent on a primary key.
Second Normal Form (2NF)
A tabular array is said to move inwards 2d Normal Form(2NF) if each tape is inwards the tabular array is inwards the First Normal form(1NF) together with each column inwards the tape is fully dependent on its primary key.
A tabular array is inwards 2d Normal Form if:
(a) It is inwards 1st Normal Form.
(b) If no non-key attribute is dependent on a constituent of composite key( combination of 2 or to a greater extent than attributes declared equally primary key), that is all the attributes must move dependent on the whole composite key non merely a constituent of it.
Note: 2d Normal Form tin move applied only to the tabular array which has whatever composite key.
Third Normal Form (3NF)
Table is said to move inwards third Normal Form when all the transitive dependencies are removed from the data.
Transitive dependency is the dependency of a non-key attribute on merely about other non-key attribute of the table.
A tabular array is said to move inwards 3NF if:
(a) It is inwards 2NF.
(b) It doesn't contain whatever transitive dependencies.
There are for certain situations when normalization tin move avoided. Those situations are equally follows:
(a) There is/are no repeating group/groups inwards the table.
(b) Influenza A virus subtype H5N1 primary key is defined.
(c) All non-key attributes are fully dependent on key attribute(primary key) or key attributes (composite key).
(d) There is no transitive dependencies.
Boyce Codd Normal Form (BCNF): Influenza A virus subtype H5N1 relation is said to move inwards BCNF if together with only if the determinants are candidate keys. BCNF relation is a potent 3NF, but non every 3NF relation is BCNF.
Sumber http://www.gcreddy.com/
Introduction:
RDBMS is a term used to depict an entire suite of programs for both managing a relational database together with communicating with that relational database engine. Sometimes Software Development Kit (SDK) front-end tools together with consummate administration kits are included with relational database packages (eg: MS Access) In other words, an RDBMS is both the database engine together with whatever other tools that come upward with it.
What is RDBMS?
RDBMS stands for Relational Database Management System. RDBMS information is structured inwards database tables, fields together with records. Each RDBMS tabular array consists of database tabular array rows. Each database tabular array row consists of 1 or to a greater extent than database tabular array fields.
RDBMS shop the information into collection of tables, which mightiness move related yesteryear mutual fields (database tabular array columns). RDBMS also render relational operators to manipulate the information stored into the database tables. Most RDBMS usage SQL equally database inquiry language.
RDBMS CONCEPTS:
What is database?
A database is a logically coherent collection of information with merely about inherent meaning, representing merely about facial expression of existent basis together with which is designed, built together with populated with information for a specific purpose.
What is DBMS?
It is a collection of programs that enables user to create together with hold a database. In other words it is general-purpose software that provides the users with the processes of defining, constructing together with manipulating the database for diverse applications.
What is a Database system?
The database together with DBMS software together is called equally Database system.
Disadvantage inwards File Processing System
Data redundancy & inconsistency.
Difficult inwards accessing data.
Data isolation.
Data integrity.
Concurrent access is non possible.
Security Problems.
Describe the 3 levels of information abstraction
The are 3 levels of abstraction:
Physical level: The lowest degree of abstraction describes how information are stored.
Logical level: The side yesteryear side higher degree of abstraction, describes what information are stored inwards database together with what human relationship with those data.
View level: The highest degree of abstraction describes only constituent of entire database.
What is System R? What are its 2 major subsystems?
System R was designed together with developed over a menstruum of 1974-79 at IBM San Jose Research Center. It is a epitome together with its purpose was to demonstrate that it is possible to build a Relational System that tin move used inwards a existent life surroundings to solve existent life problems, with performance at to the lowest degree comparable to that of existing system.
Its 2 subsystems are
Research Storage
System Relational Data System.
How is the information construction of System R dissimilar from the relational structure
Unlike Relational systems inwards System R
Domains are non supported
Enforcement of candidate key uniqueness is optional
Enforcement of entity integrity is optional
Referential integrity is non enforced
What is Data Independence
Data independence agency that 'the application is independent of the storage construction together with access strategy of data'. In other words, The powerfulness to modify the schema Definition inwards 1 degree should non impact the schema Definition inwards the side yesteryear side higher level.
Two types of Data Independence:
Physical Data Independence: Modification inwards physical degree should non impact the logical level.
Logical Data Independence: Modification inwards logical degree should impact the sentiment level.
NOTE: Logical Data Independence is to a greater extent than hard to achieve
What is a view?How it is related to information independence
A sentiment may move idea of equally a virtual table, that is, a tabular array that does non actually be inwards its ain correct but is instead derived from 1 or to a greater extent than underlying base of operations table. In other words, at that spot is no stored file that straight represents the sentiment instead a Definition of sentiment is stored inwards information dictionary. Growth together with restructuring of base of operations tables is non reflected inwards views. Thus the sentiment tin insulate users from the effects of restructuring together with increment inwards the database. Hence accounts for logical information independence.
What is Data Model?
A collection of conceptual tools for describing data, information relationships information semantics together with constraints.
What is E-R model
This information model is based on existent basis that consists of basic objects called entities together with of human relationship with these objects. Entities are described inwards a database yesteryear a laid upward of attributes
The Entity-Relationship information model is based on a perception of the existent basis which consists of basic objects called entities together with relationships with theseobjects.
Key:
Influenza A virus subtype H5N1 key is an attribute or laid upward of attributes of an entitywhich tin move used to seat it.
Super Keyis a laid upward of 1 or to a greater extent than attributes which, takencollectively, allows an entity to be uniquelyidentified inwards an entity set
Candidate Keyis a super key for which no proper subset is a superkey (i.e., a minimal super key)
Primary Keyis a candidate key chosen yesteryear the database designeras the regulation agency of identifying entities withinan entity set.
ER Model: Constraints
Constraints:
Key Constraints: These are constraints implied yesteryear the beingness of candidate keys. The tabular array Definition includes aspecification implying uniqueness of the attributesconstituting the primary key or alternate keys.
Influenza A virus subtype H5N1 primary key constraint also implies a no-nulls constraint.Referential Constraints:Constraints implied yesteryear the beingness of unusual keys inthe tabular array definition.Other Constraints:Constraints enforcing checks of delineate of piece of job organisation logic of theapplication inwards the tabular array definition.
Features of RDBMS
Relational database administration organisation has diverse next features:-
1-It tin solve whatever complex queries.
2-RDBMS is really secure.A fully RDBMS tin forestall from whatever unauthorized access.
Advantages of RDBMS over DBMS:
• Reliability is improved because the information is non spread across the network together with several applications. Only 1 procedure handles the data.
• Network traffic is greatly reduced. Let’s tell inwards desktop database model – entire database along with indexes is to move sent to client. Where equally inwards Client/server database model only outcome is to move sent to client.
• Upgrading a heavily used desktop database to a well-designed client/server database volition cut database-related network traffic yesteryear to a greater extent than than 95%.
• Performance is improved equally database operations are handled over server, therefore customer PCs volition receive got less processing requirement.
• Security is improved equally information are kept inside a unmarried server. Hacking into a information file that is protected inside the server is much to a greater extent than hard than hacking into a information file on desktop database model.
• Data integrity constraints together with delineate of piece of job organisation rules tin move enforced at server level. You tin specify rules such equally “Marks of whatever plain of report tin non hap 100 inwards whatever subject”
• Data Sharing: SQL is used to coordinate information sharing yesteryear concurrent users, ensuring that they produce non interfere with 1 another.
• Data tin move integrated using multiple platform i.e. LAN, WAN together with WAN. One tin contain information from INTERNET
CODD Rules:
A relational database administration organisation (RDBMS) is a database administration organisation (DBMS) that is based on the relational model equally introduced yesteryear E. F. Codd. Most pop commercial together with opened upward rootage databases currently inwards usage are based on the relational model.
A curt Definition of an RDBMS may move a DBMS inwards which information is stored inwards the sort out of tables together with the human relationship with the information is also stored inwards the sort out of tables.
E.F. Codd, the famous mathematician has introduced 12 rules for the relational model for databases usually known equally Codd's rules. The rules mainly define what is required for a DBMS for it to move considered relational, i.e., an RDBMS. There is also 1 to a greater extent than dominion i.e. Rule00 which specifies the relational model should usage the relational way to create out the database. The rules together with their description are equally follows:-
Rule 0: Foundation Rule
A relational database administration organisation should move capable of using its relational facilities (exclusively) to create out the database.
Rule 1: Information Rule
All information inwards the database is to move represented inwards 1 together with only 1 way. This is achieved yesteryear values inwards column positions inside rows of tables.
Rule 2: Guaranteed Access Rule
All information must move accessible with no ambiguity, that is, Each together with every datum (atomic value) is guaranteed to move logically accessible yesteryear resorting to a combination of tabular array name, primary key value together with column name.
Rule 3: Systematic handling of zilch values
Null values (distinct from empty grapheme string or a string of blank characters together with distinct from null or whatever other number) are supported inwards the fully relational DBMS for representing missing information inwards a systematic way, independent of information type.
Rule 4: Dynamic On-line Catalog Based on the Relational Model
The database description is represented at the logical degree inwards the same way equally ordinary data, therefore authorized users tin apply the same relational linguistic communication to its interrogation equally they apply to regular data. The authorized users tin access the database construction yesteryear using mutual linguistic communication i.e. SQL.
Rule 5: Comprehensive Data Sublanguage Rule
A relational organisation may back upward several languages together with diverse modes of final use. However, at that spot must move at to the lowest degree 1 linguistic communication whose statements are expressible, per merely about well-defined syntax, equally grapheme strings together with whose powerfulness to back upward all of the next is comprehensible:
a. information definition
b. sentiment definition
c. information manipulation (interactive together with yesteryear program)
d. integrity constraints
e. authorization
f. Transaction boundaries (begin, commit, together with rollback).
Rule 6: View Updating Rule
All views that are theoretically updateable are also updateable yesteryear the system.
Rule 7: High-level Insert, Update, together with Delete
The organisation is able to insert, update together with delete operations fully. It tin also perform the operations on multiple rows simultaneously.
Rule 8: Physical Data Independence
Application programs together with final activities rest logically unimpaired whenever whatever changes are made inwards either storage representation or access methods.
Rule 9: Logical Data Independence
Application programs together with final activities rest logically unimpaired when information preserving changes of whatever form that theoretically permit unimpairment are made to the base of operations tables.
Rule 10: Integrity Independence
Integrity constraints specific to a item relational database must move definable inwards the relational information sublanguage together with storable inwards the catalog, non inwards the application programs.
Rule 11: Distribution Independence
The information manipulation sublanguage of a relational DBMS must enable application programs together with final activities to rest logically unimpaired whether together with whenever information are physically centralized or distributed.
Rule 12: Nonsubversion Rule
If a relational organisation has or supports a low-level (single-record-at-a-time) language, that low-level linguistic communication cannot move used to subvert or bypass the integrity rules or constraints expressed inwards the higher-level (multiple-records-at-a-time) relational language.
Normalization:
• Normalisation is a blueprint techniques that is widely used equally guide inwards designing relational database.
• It is a two-step procedure that puts information into tabular sort out yesteryear removing repeating groups emmet therefore removes duplicated information from relational table.
• Thus Normalisation is the procedure of structuring an unstructured relation into structural 1 with the purpose of removing redundancy together with anomalies.
• Normalisation theory is based on normal forms.A relational tabular array is said to move item normal forms if it satisfy a for certain laid upward of constraints.
Functional Dependency : It depict the human relationship betwixt 2 attributes of same relational database tables.One of the attributes is called determinant together with other attribute is called determined.
For eg.- For each value of determinant at that spot is associated 1 together with only 1 value of determined.
Influenza A virus subtype H5N1 -> B
The Influenza A virus subtype H5N1 is determinant together with B is determined therefore nosotros tell that Influenza A virus subtype H5N1 functionally determines B or Bis functionally dependent on A.
Fully Functional Dependence : It states that if Influenza A virus subtype H5N1 together with B are 2 attributes of a relation therefore B is Fully Functionaly Dependent on Influenza A virus subtype H5N1 if B is Functional Dependent on Influenza A virus subtype H5N1 together with non a proper subset of A.
Transitive Dependency : If Bis functional Dependent on Influenza A virus subtype H5N1 together with C is functional dependent on B therefore C is transitive dependent on A.
The next are the types of normal forms:
First Normal Form (1NF)
When a tabular array is broken upward (decomposed)into to a greater extent than tables with all repeating groups(records) of information eliminated, tabular array information is said to move inwards the commencement normal sort out (1NF).
A tabular array is said to move inwards 1st Normal sort out if:
(a) There is no repeating group.
(b) All the key attributes are defined.
(c) All the non-key attributes are dependent on a primary key.
Second Normal Form (2NF)
A tabular array is said to move inwards 2d Normal Form(2NF) if each tape is inwards the tabular array is inwards the First Normal form(1NF) together with each column inwards the tape is fully dependent on its primary key.
A tabular array is inwards 2d Normal Form if:
(a) It is inwards 1st Normal Form.
(b) If no non-key attribute is dependent on a constituent of composite key( combination of 2 or to a greater extent than attributes declared equally primary key), that is all the attributes must move dependent on the whole composite key non merely a constituent of it.
Note: 2d Normal Form tin move applied only to the tabular array which has whatever composite key.
Third Normal Form (3NF)
Table is said to move inwards third Normal Form when all the transitive dependencies are removed from the data.
Transitive dependency is the dependency of a non-key attribute on merely about other non-key attribute of the table.
A tabular array is said to move inwards 3NF if:
(a) It is inwards 2NF.
(b) It doesn't contain whatever transitive dependencies.
There are for certain situations when normalization tin move avoided. Those situations are equally follows:
(a) There is/are no repeating group/groups inwards the table.
(b) Influenza A virus subtype H5N1 primary key is defined.
(c) All non-key attributes are fully dependent on key attribute(primary key) or key attributes (composite key).
(d) There is no transitive dependencies.
Boyce Codd Normal Form (BCNF): Influenza A virus subtype H5N1 relation is said to move inwards BCNF if together with only if the determinants are candidate keys. BCNF relation is a potent 3NF, but non every 3NF relation is BCNF.