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In the context of data models, cardinality means the relationship between two tables.

• One to One:-One row of the first table partners with one row of the second table
• One to Many:-One row of the first table partners with more than one rows of the second table
• Many to One:-More than one rows of the first table partners with one row of the second table
• Many to Many:-More than one rows of the first table partners with more than one rows of the second table

In the context of Query OPTIMIZATION, Cardinality refers to the uniqueness of the COLUMN in the table. A column having unique value will have high cardinality and vice-versa.

In LOGICAL DATA Independence the logical schema is modified without rewriting the APPLICATION programs whereas in Physical Data Independence the physical schema is changed without rewriting the application programs.

• Super Key:- This key RECOGNIZES the row in the table.
• Primary Key:-This key is a column in the table which recognizes each row in the same table uniquely
• Candidate Key:-This key does not have any repeated attribute
• Foreign Key:-This key a column in the table to CREATE a relationship with another table.

This particular RDBMS Question explains the IMPORTANCE of KEYS in the DATABASE.

Codd's rules or Codd's law are the set of 12 states which was developed by E.F. Codd in the year 1969-1970. Codd's law tells what is required from the database management system so that it can be considered relational.in other words, Codd's rules are rules for designing the RDBMS.

• Rule 1: INFORMATION rule:-All the information has to be represented in only one way in the table
• Rule 2:Guaranteed Access:-Every value in the table has to be accessible by the Table Name + Primary Key(Row) + Attribute(column).
• Rule 3: Systematic TREATMENT of NULL:-NULL values should be TREATED systematically
• Rule 4: Active Online Catalog:-The catalog must be stored online
• Rule 5: Powerful and Well-Structured Language: -A structured language should provide all access to the data which is stored in the database.
• Rule 6: View Updation Rule:-All the view has to be updatable by the database system
• Rule 7: Relational Level Operation:-There has to be the Insert, Delete, Update operations at every level of the relations
• Rule 8: Physical Data Independence:-The changes in the Physical storage of the data should not affect the database system.
• Rule 9: Logical Data Independence:-The changes in the logical structure of the database should not change the user view of the data.
• Rule 10: Integrity Independence:-The Key and the Check constraints, the trigger, ETC., should be stored in the Data Dictionary.
• Rule 11: Distribution Independence: -A database should work correctly even if it is distributed across the network
• Rule 12:Nonsubversion Rule:-If the low-level access has been allowed to a system; then it should not be able to subvert the integrity rules to alter the data.

An Entity-Relationship model is primarily used to REPRESENT the real scenarios as entities. E-R model clearly defines the OBJECTS and the relations between the entities

An Object-oriented Model is mainly used to represent the real scenarios as objects. The objects with similar functions are grouped and linked to the other DIFFERENT purposes.in this model, the data can be reused in various missions.

Note:-This is the important RDBMS INTERVIEW questions.

• RDBMS handles a LARGE quantity of DATA.
• RDBMS has very high-end security
• RDBMS supports client-server architecture
• RDBMS supports multiple users
• RDBMS has MINIMUM data redundancy

• It can be used by more than one USERS at the same time
• Reduces the DATA REDUNDANCY and data duplication
• RDBMS provided MULTIPLE interfaces
• RDBMS is SECURE

RDBMS stands for the Relational DATABASE Management System.RDBMS is the DBMS in which the data is stored in the tables, i.e., the values are stored in the rows and columns.

• Tables:-Table HOLDS the records for one entity WHOSE information has to be saved. Here every row contains a record, and every column represents an attribute.
• Forms:-Forms are used to enter the new record into the database.
• Queries:-Queries are used to search the data across the tables to executes the queries.
• Reports:-Reports are used to organize the query results in a proper way.
• Macros:-PROVIDES the more features and the extra functionality to the database.
• Modules:-Programmers can write the modules in their respective programming language and then run the blades when they are required from the database.