I have search for information about the difference between unique index
and unique constraint in PostgreSQL without getting to a specific answer,
so I kindly ask for an explanation that helps me clarify such concept.
Respectfully,
Jorge Maldonado
Il 04/10/2013 18:48, JORGE MALDONADO ha scritto:
I have search for information about the difference between unique
index and unique constraint in PostgreSQL without getting to a
specific answer, so I kindly ask for an explanation that helps me
clarify such concept.
2 main differences.
First
On 10/04/2013 09:48 AM, JORGE MALDONADO wrote:
I have search for information about the difference between unique
index and unique constraint in PostgreSQL without getting to a
specific answer, so I kindly ask for an explanation that helps me
clarify such concept.
The way I think of it is, that
On 10/04/2013 10:41 AM, luca...@gmail.com wrote:
Il 04/10/2013 18:48, JORGE MALDONADO ha scritto:
I have search for information about the difference between unique
index and unique constraint in PostgreSQL without getting to a
specific answer, so I kindly ask for an explanation that helps me
I have a table with fields that I guess would be a good idea to set as
indexes because users may query it to get results ordered by different
criteria. For example:
--
Artists Table
--
1. art_id
2. art_name
3. art_bday
4. art_sex
5. art_country (foreign key, there
JORGE MALDONADO wrote
I have a table with fields that I guess would be a good idea to set as
indexes because users may query it to get results ordered by different
criteria. For example:
--
Artists Table
--
1. art_id
2. art_name
3. art_bday
4. art_sex
I really appreciate your fast and very complete answer.
If a table has a foreign key on 2 fields, should I also create an index
composed of such fields?
For example:
---
Table Sources
---
1. src_id
2. src_date
3. Other fields . . .
Here, the primary key
JORGE MALDONADO wrote
I have search for information about the difference between unique index
and unique constraint in PostgreSQL without getting to a specific
answer,
so I kindly ask for an explanation that helps me clarify such concept.
A constraint says what valid data looks like.
An
JORGE MALDONADO wrote
If a table has a foreign key on 2 fields, should I also create an index
composed of such fields?
Yes.
If you want to truly/actually model a foreign key the system will require
you to create a unique constraint/index on the primary/one side of the
relationship.
CREATE
Unique indexes can be partial, i.e. defined with a where clause (that must
be included in a query so that PostgreSQL knows to use that index) whereas
unique constraints cannot.
JORGE MALDONADO wrote
I have search for information about the difference between unique index
and unique constraint in
Steve Grey-2 wrote
Unique indexes can be partial, i.e. defined with a where clause (that must
be included in a query so that PostgreSQL knows to use that index) whereas
unique constraints cannot.
This implies there can be data in the table but not in the index and thus
said index is not part
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