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I have a table with some columns, now i need to modify one column to make it unique(no duplicate values), how can i do that in ruby on rails?
926
Unique indexes are indexes that help maintain data integrity by ensuring that no rows of data in a table have identical key values. When you create a unique index for an existing table with data, values in the columns or expressions that comprise the index key are checked for uniqueness.
PostgreSQL automatically creates a unique index when a unique constraint or primary key is defined for a table. The index covers the columns that make up the primary key or unique constraint (a multicolumn index, if appropriate), and is the mechanism that enforces the constraint.
Migrations are a convenient way to alter your database schema over time in a consistent way. They use a Ruby DSL so that you don't have to write SQL by hand, allowing your schema and changes to be database independent. You can think of each migration as being a new 'version' of the database.
You can add a validation to your model to forbid duplicated values
class MyModel < ActiveRecord::Base
validates_uniqueness_of :my_column_name
end
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