五范式(国外英文资料).docVIP

五范式(国外英文资料) Detailed database paradigm: third paradigms and fifth paradigm in 2009 01 on Friday 16 June 8:53 A.M.1NF: a table column is not divided (i.e. column atomic) 2NF: a table line is only marked (i.e., table line can not be repeated) 3NF: a table column does not rely on non primary key columns in another table, or not popular! Huge cold!! For example: there is a division of the table, we call it tbl_department, it has so few columns (dept_id (PK), dept_name, dept_memo...) There is a staff of table, we call it tbl_employee, a list of dept_id in the table (FK) a description of the Department of information, if the tbl_employee to meet 3NF, The tbl_employee will not be listed in other relevant departments except dept_id information column! Design of general database can meet 3NF! (personally think it should be possible to meet the 3NF statements of a school, ^_^) BCNF: BCNF is considered as the correction of the third paradigms, it further than 3NF! 4NF: 5NF: a table as much as possible is divided into small blocks, to eliminate all redundant data in table Brief introduction of paradigm In order to answer the above questions, understand the difference between 3NF, BCNF, 4NF and 5NF is very important. The accurate definition of each paradigm. The first paradigm (1NF) Each table must have a primary key, which is a minimal set of attribute, which correspond to each record. By defining the key attribute and non key attributes, delete duplicate groups (different records seem to require different repetitive data types). Note: each property must contain a single value, rather than a set of values. The second paradigm (2NF) The database must satisfy all the requirements of 1NF. In addition, if a table has a composite key, all attributes must be associated with the key. Also, unnecessary and repetitive data is moved in a separate table between the rows of the table. The third paradigm (3NF) The data stored in the table may not be any domain dependency table, must only de