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data:modeling:foreign_key [2012/04/03 14:03]
data:modeling:foreign_key [2019/08/13 09:32] (current)
gerardnico [1 - About]
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 ===== About ===== ===== About =====
-A Foreign Key (also known as as foreign key [[constraint|constraint]]) is:+A Foreign Key is a [[constraint|constraint]] ​on :
   * a column ​   * a column ​
   * or combination of columns ​   * or combination of columns ​
-used to establish and enforce a [[relationship|relationship]] between data in two tables. ​+used to establish and enforce a [[relationship|relationship ​(link)]] between data in two tables. ​
-Usually the foreign key is coupled with the [[primary key|primary key]] of the other table.+The link is created between ​the two tables by adding the column or columns that hold one table'​s ​[[primary key|primary key]] values 
 +to the other table. This column becomes a Foreign Key in the second table.  
 +A foreign key may be enforced, e.g. by a foreign key constraint. 
 +[[Referential Integrity|Referential Integrity]] is a data property whereby a Foreign Key in one table has a corresponding Primary key in a different ​table.
data/modeling/foreign_key.1333454621.txt.gz · Last modified: 2012/04/03 14:03 by gerardnico