Adding a forging key to tables in Netezza / PureData is a best practice; especially, when working with dimensionally modeled data warehouse structures and with modern governance, integration (including virtualization), presentation semantics (including reporting, business intelligence and analytics).
Foreign Key (FK) Guidelines
A primary key must be defined on the table and fields (or fields) to which you intend to link the foreign key
Avoid using distribution keys as foreign keys
Foreign Key field should not be nullable
Your foreign key link field(s) must be of the same format(s) (e.g. integer to integer, etc.)
Apply standard naming conventions to constraint name:
FK_<<Constraint_Name>>_<<Number>>
<<Constraint_Name>>_FK<<Number>>
Please note that foreign key constraints are not enforced in Netezza
Steps to add a Foreign Key
The process for adding foreign keys involves just a few steps:
Verify guidelines above
Alter table add constraint SQL command
Run statistics, which is optional, but strongly recommended
Basic Foreign Key SQL Command Structure
Here is the basic syntax for adding Foreign key:
ALTER TABLE <<Owner>>.<<NAME_OF_TABLE_BEING_ALTERED>>
ADD CONSTRAINT <<Constraint_Name>>_fk<Number>>
FOREIGN KEY (<<Field_Name or Field_Name List>>) REFERENCES <<Owner>>.<<target_FK_Table_Name>.(<<Field_Name or Field_Name List>>) <<On Update | On Delete>> action;
Example Foreign Key SQL Command
This is a simple one field example of the foreign key (FK)
ALTER TABLE Blog.job_stage_fact
ADD CONSTRAINT job_stage_fact_host_dim_fk1
FOREIGN KEY (hostid) REFERENCES Blog.host_dim(hostid) ON DELETE cascade ON UPDATE no action;
Related References
Alter Table
PureData System for Analytics, PureData System for Analytics 7.2.1, IBM Netezza database user documentation, Netezza SQL command reference, Alter Table, constraints
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