What are different normalization forms?

What are different normalization forms?

1NF: Eliminate Repeating Groups
Make a separate table for each set of related attributes, and give each table a primary key. Each field
contains at most one value from its attribute domain.

2NF: Eliminate Redundant Data
If an attribute depends on only part of a multi-valued key, remove it to a separate table.

3NF: Eliminate Columns Not Dependent On Key
If attributes do not contribute to a description of the key, remove them to a separate table. All
attributes must be directly dependent on the primary key

BCNF: Boyce-Codd Normal Form
If there are non-trivial dependencies between candidate key attributes, separate them out into distinct
tables.

4NF: Isolate Independent Multiple Relationships
No table may contain two or more 1:n or n:m relationships that are not directly related.

5NF: Isolate Semantically Related Multiple Relationships
There may be practical constrains on information that justify separating logically related many-to-many
relationships.

ONF: Optimal Normal Form
A model limited to only simple (elemental) facts, as expressed in Object Role Model notation.

DKNF: Domain-Key Normal Form
A model free from all modification anom

Comments

Post a Comment

Popular posts from this blog

What is the use of DBCC commands?

What is the use of DBCC commands? DBCC stands for database consistency checker. We use these commands to check the consistency of the databases, i.e., maintenance, validation task and status checks. E.g. DBCC CHECKDB - Ensures that tables in the db and the indexes are correctly linked. DBCC CHECKALLOC - To check that all pages in a db are correctly allocated. DBCC CHECKFILEGROUP - Checks all tables file group for any damage.
Read more

Google to FTS Syntax Cheat Sheet

Image
OPERATOR EXAMPLE DESCRIPTION   nut Searches for inflectional forms of the word nut crank arm crank AND arm Searches for documents containing inflectional forms of the words crank AND arm crank and ann. The keyword AND is optional. tire OR air Searches for documents containing inflectional forms of the words tire or air, “reflector bracket” Performs a phrase search for the phrase "reflector bracket". hardware -bracket Searches for documents containing inflectional forms of the word hardware but not the word bracket. +clamp Searches for the word darn') without generating inflectional forms. ~seat Searches for thesaurus forms of the word seat Assemb* Searches for words that begin with the prefix assemb . <washer nut> Searches for documents that contain the words washer in close proximity to the word nut
Read more

What is difference between DELETE and TRUNCATE commands?

Delete command removes the rows from a table based on the condition that we provide with a WHERE clause. Truncate will actually remove all the rows from a table and there will be no data in the table after we run the truncate command. TRUNCATE : TRUNCATE is faster and uses fewer system and transaction log resources than DELETE. TRUNCATE removes the data by deallocating the data pages used to store the table's data, and only the page deallocations are recorded in the transaction log. TRUNCATE removes all rows from a table, but the table structure, its columns, constraints, indexes and so on, remains. The counter used by an identity for new rows is reset to the seed for the column. You cannot use TRUNCATE TABLE on a table referenced by a FOREIGN KEY constraint. Because TRUNCATE TABLE is not logged, it cannot activate a trigger. TRUNCATE cannot be rolled back. TRUNCATE is DDL Command. TRUNCATE Resets identity of the table DELETE : DELETE removes rows one at a time...
Read more