The unique-key tag has no wiki summary.
9
votes
3answers
4k views
PostgreSQL multi-column unique constraint and NULL values
I have a table like the following:
create table my_table (
id int8 not null,
id_A int8 not null,
id_B int8 not null,
id_C int8 null,
constraint pk_my_table primary key (id),
constraint ...
16
votes
3answers
5k views
When should I use a unique constraint instead of a unique index?
When I want a column to have distinct values, I can either use a constraint
create table t1(
id int primary key,
code varchar(10) unique NULL
);
go
or I can use a unique index
create table t2(
id ...
4
votes
2answers
128 views
Custom unique column constraint, only enforced if one column has a specific value
Is it possible to have a custom unique column constraint as follows? Suppose I have two cols, subset and type, both strings (though the data types probably doesn't matter).
If type is "true", then ...
2
votes
3answers
621 views
Unique combination key MySQL
Lets say I have a table with 3 fields:
id1
id2
mapTypeId
What I want is a primary/unique key that is any combination of id1 and id2. For example if I have this record already in the database:
...
4
votes
1answer
3k views
Optimal way to ignore duplicate inserts?
Background
This problem relates to ignoring duplicate inserts using PostgreSQL 9.2 or greater. The reason I ask is because of this code:
-- Ignores duplicates.
INSERT INTO
db_table ...
1
vote
2answers
255 views
Best type to use in a composite key when one of the values varies in type
I am building a data store for the content of multiple blog sites which have been scraped. Each of these sites is going to have an entry in a Blog table
BlogId Url ...
