![]() ![]() remove_check_constraint (must supply original constraint expression).drop_table (must supply table creation options and block).change_table_comment (must supply :from and :to options).change_column_default (must supply :from and :to options).change_column_comment (must supply :from and :to options).Below are some of the actions that change supports: Majority of cases in which Active Record knows how to reverse a migration'sĪctions automatically. The change method is the primary way of writing migrations. execute ( "UPDATE products SET price = 'free' WHERE 1=1" ) Copyįor more details and examples of individual methods, check the API documentation.ĪctiveRecord::ConnectionAdapters::SchemaStatements, which provides the methods available in the change, up and down methods.įor methods available regarding the object yielded by create_table, see ActiveRecord::ConnectionAdapters::TableDefinition.Īnd for the object yielded by change_table, see ActiveRecord::ConnectionAdapters::Table. ![]() Representing the number of digits after the decimal point. scale Specifies the scale for the decimal and numeric columns,.precision Specifies the precision for decimal/numeric/datetime/time columns. ![]() null Allows or disallows NULL values in the column.limit Sets the maximum number of characters for a string columnĪnd the maximum number of bytes for text/binary/integer columns.Note that if youĪre using a dynamic value (such as a date), the default will only be calculated default Allows to set a default value on the column.collation Specifies the collation for a string or text column.3.5 Column ModifiersĬolumn modifiers can be applied when creating or changing a column: ![]() You could also write the above change_column_default migration asĬhange_column_default :products, :approved, false, but unlike the previousĮxample, this would make your migration irreversible. You will have to rollback the changes that were made by hand. Then when a migration fails the parts of it that succeeded will not be rolledīack. On databases that support transactions with statements that change the schema,Įach migration is wrapped in a transaction. This migration back, it will remove the table. Active Record knows how to reverse this migration as well: if we roll Note that we define the change that we want to happen moving forward in time.īefore this migration is run, there will be no table. These special columns are automatically managed by Active Record The timestamps macro adds two columns, created_at and Will also be added implicitly, as it's the default primary key for all Active Name and a text column called description. This migration adds a table called products with a string column called
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