DR .E.F codd ( Edgar Frank Codd) in his RDBMS specifications has proposed a set of roles that has to be satisfied by data base to be called as relational and we call those rule as codd rules in sql server.
There are 12 codd rules in sql server which are proposed by codd and any database will be call as relational needs to satisfy at least six of the available rules.
According to this data under a relational data base must be stored in the form of a table that is data in the form of rows and columns.
according to this every row of the table must have a unique identification for accessing the row. So that we can easily pick the desired in the table which doesn’t contain (or) allow duplicates and NULL values and we call that column as a identity column.
according to this a data base should allow storing of null values under a column of a table provided the value is unknown and this NULL value should be capable of being stored under any data typed column like a string or into or float or Boolean.
– The information base portrayal is spoken to at the legitimate level similarly as customary information, with the goal that approved clients can apply an indistinguishable social dialect to its cross examination from they apply to the consistent information.
A database must be gotten to utilizing a dialect having straight language structure that backings information definition, information control, and exchange administration operations. This dialect can be utilized specifically or by methods for some application. In the event that the database enables access to information with no assistance of this dialect, at that point it is considered as an infringement.
A view is a logical table which is used for maintaining multiple copies of the data without Redundancy. The best thing in a view is any modification we perform on the table reflects into the view. According to the view update rule the views which are displaying the data should also be updatable and those changes must be reflected back into the table.
A database must help abnormal insertion, update, and deletion. This must not be constrained to a solitary column, that is, it should likewise bolster union, crossing point and less operations to yield sets of information records.
The information put away in a database must be autonomous of the applications that entrance the database. Any adjustment in the physical structure of a database must not have any effect on how the information is being gotten to by outer applications.
The consistent information in a database must be free of its client's view (application). Any change in coherent information must not influence the applications utilizing it. For instance, if two tables are consolidated or one is part into two unique tables, there ought to be no effect or change on the client application. This is a standout amongst the most troublesome lead to apply.
A database must be autonomous of the application that utilizations it. All its honesty requirements can be freely altered without the need of any adjustment in the application. This lead makes a database autonomous of the front-end application and its interface.
The end-client must not have the capacity to see that the information is dispersed over different areas. Clients ought to dependably get the feeling that the information is situated at one site as it were. This manage has been viewed as the establishment of conveyed database frameworks.
In the event that a framework has an interface that gives access to low-level records, at that point the interface must not have the capacity to subvert the framework and sidestep security and honesty imperatives.