2013/7/27 Alvaro Herrera
>
> PostgreSQL implements unique constraints by way of unique indexes (and
> it's likely that all RDBMSs do likewise). Also, the syntax to declare
> unique indexes allows for more features than the unique constraints
> syntax. For example, you can have a unique index tha
On Fri, Jul 26, 2013 at 3:19 PM, Alvaro Herrera
wrote:
> JORGE MALDONADO escribió:
>> I guess I am understanding that it is possible to set a unique index or a
>> unique constraint in a table, but I cannot fully understand the difference,
>> even though I have Google some articles about it. I will
JORGE MALDONADO escribió:
> I guess I am understanding that it is possible to set a unique index or a
> unique constraint in a table, but I cannot fully understand the difference,
> even though I have Google some articles about it. I will very much
> appreciate any guidance.
The SQL standard does
I try to explain my point of view, also in my not so good English:
A primary key is defined by dr. Codd in relational model.
The key is used to identify a record. In good practice, you must always
define a primary key. Always.
The unique constraint will simply say: this value (or combination) shou
I guess I am understanding that it is possible to set a unique index or a
unique constraint in a table, but I cannot fully understand the difference,
even though I have Google some articles about it. I will very much
appreciate any guidance.
Respectfully,
Jorge Maldonado
