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Ecto migrations automatically create an auto increment field by name 'id' in the table.
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No. A primary key must be unique and that has to be 100% guaranteed, and NON NULL A primary key should be stable if ever possible and not change.
The MS SQL Server uses the IDENTITY keyword to perform an auto-increment feature. In the example above, the starting value for IDENTITY is 1, and it will increment by 1 for each new record. Tip: To specify that the "Personid" column should start at value 10 and increment by 5, change it to IDENTITY(10,5) .
By simply setting our id column as SERIAL with PRIMARY KEY attached, Postgres will handle all the complicated behind-the-scenes work and automatically increment our id column with a unique, primary key value for every INSERT .
In MySQL, the syntax to change the starting value for an AUTO_INCREMENT column using the ALTER TABLE statement is: ALTER TABLE table_name AUTO_INCREMENT = start_value; table_name. The name of the table whose AUTO_INCREMENT value you wish to change.
You can opt out of the automatically generated primary key column with the primary_key: false option to table/2. You can set another column as primary key with the primary_key: true option to add/3:
create table(:users, primary_key: false) do
add :my_id, :integer, primary_key: true
add :name, :string
# ...
end
For more info, please refer to the documentation:
http://hexdocs.pm/ecto/0.11.3/Ecto.Migration.html#table/2 http://hexdocs.pm/ecto/0.11.3/Ecto.Migration.html#add/3
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