StackOverflow2013

Note that there are some explanatory texts on larger screens.

plurals

PO
text
Body
copied!<p>Normalization is not for MYSql only. Its a general database concept.</p> <blockquote> <p>Normalization is the process of efficiently organizing data in a database. There are two goals of the normalization process: eliminating redundant data (for example, storing the same data in more than one table) and ensuring data dependencies make sense (only storing related data in a table). Both of these are worthy goals as they reduce the amount of space a database consumes and ensure that data is logically stored.</p> </blockquote> <p>Normal forms in SQL are given below.</p> <blockquote> <p>First Normal form (1NF): A relation is said to be in 1NF if it has only single valued attributes, neither repeating nor arrays are permitted.</p> <p>Second Normal Form (2NF): A relation is said to be in 2NF if it is in 1NF and every non key attribute is fully functional dependent on the primary key.</p> <p>Third Normal Form (3NF): We say that a relation is in 3NF if it is in 2NF and has no transitive dependencies.</p> <p>Boyce-Codd Normal Form (BCNF): A relation is said to be in BCNF if and only if every determinant in the relation is a candidate key.</p> <p>Fourth Normal Form (4NF): A relation is said to be in 4NF if it is in BCNF and contains no multivalued dependency.</p> <p>Fifth Normal Form (5NF): A relation is said to be in 5NF if and only if every join dependency in relation is implied by the candidate keys of relation.</p> <p>Domain-Key Normal Form (DKNF): We say that a relation is in DKNF if it is free of all modification anomalies. Insertion, Deletion, and update anomalies come under modification anomalies</p> </blockquote> <p>Seel also</p> <p><a href="http://databases.about.com/od/specificproducts/a/normalization.htm" rel="noreferrer">Database Normalization Basics</a></p>

Querying!

Guidance

An individual column

Larger individual text columns get their own page to allow for proper reading.

SQuiL has stopped working due to an internal error.

If you are curious you may find further information in the browser console, which is accessible through the devtools (F12).

Reload