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data:modeling:foreign_key [2010/05/24 20:56]
data:modeling:foreign_key [2019/08/13 09:32] (current)
gerardnico [1 - About]
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-====== Data Modeling - Foreign Key Definition ​======+====== Data Modeling - Foreign Key Constraint ​======
 ===== About ===== ===== About =====
 +A Foreign Key is a [[constraint|constraint]] on :
 +  * a column ​
 +  * or combination of columns ​
 +used to establish and enforce a [[relationship|relationship (link)]] between data in two tables. ​
 +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.
 +===== Articles Related =====
 +===== Example =====
 An Foreign Key example of a database (with the scott schema from Oracle). An Foreign Key example of a database (with the scott schema from Oracle).
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 If it's not true, there is NO [[referential_integrity|referential integrity]]. If it's not true, there is NO [[referential_integrity|referential integrity]].
-===== Articles Related ===== 
data/modeling/foreign_key.1274727418.txt.gz · Last modified: 2010/05/24 20:56 by gerardnico