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Whats the main difference between a unique key constraint and a primary key constraint?
Which is better for large partitioned tables in a data warehouse environment.
Unique key means it allows uniques values only... which means nulls too because according to Oracle each null is different from other.
Primary key means the combination of Unique key and Not null constraint.
I dont know much of dataware housing problems.... but as far as i have seen the Oracle Apps tables always use Primary key to Unique key
The main difference between Unique key and Primary key is that , Unique key is NULLABLE, while primary key is always NOT NULL.
I think Primary key is better for large partitioned tables in a DWH environment.
Diffenece b/w primary key & unique key as below :
Primary key unique with mandatory (not null. Always take value in primary key).
Unique key unique with not mandatory (null ).