ActiveRecord::ConnectionAdapters::SchemaStatements

• activerecord/lib/active_record/connection_adapters/abstract/schema_statements.rb

• add_column
• add_index
• add_order_by_for_association_limiting!
• add_timestamps
• assume_migrated_upto_version
• change_column
• change_column_default
• change_table
• columns
• create_table
• distinct
• drop_table
• initialize_schema_migrations_table
• native_database_types
• options_include_default?
• remove_column
• remove_columns
• remove_index
• remove_timestamps
• rename_column
• rename_table
• structure_dump
• table_alias_for
• table_alias_length
• table_exists?

Adds a new column to the named table. See TableDefinition#column for details of the options you can use.

Adds a new index to the table. column_name can be a single Symbol, or an Array of Symbols.

The index will be named after the table and the first column name, unless you pass :name as an option.

When creating an index on multiple columns, the first column is used as a name for the index. For example, when you specify an index on two columns [:first, :last], the DBMS creates an index for both columns as well as an index for the first column :first. Using just the first name for this index makes sense, because you will never have to create a singular index with this name.

Examples

Creating a simple index

 add_index(:suppliers, :name)

generates

 CREATE INDEX suppliers_name_index ON suppliers(name)

Creating a unique index

 add_index(:accounts, [:branch_id, :party_id], :unique => true)

generates

 CREATE UNIQUE INDEX accounts_branch_id_party_id_index ON accounts(branch_id, party_id)

Creating a named index

 add_index(:accounts, [:branch_id, :party_id], :unique => true, :name => 'by_branch_party')

generates

 CREATE UNIQUE INDEX by_branch_party ON accounts(branch_id, party_id)

ORDER BY clause for the passed order option. PostgreSQL overrides this due to its stricter standards compliance.

Adds timestamps (created_at and updated_at) columns to the named table.

Examples

 add_timestamps(:suppliers)

Changes the column‘s definition according to the new options. See TableDefinition#column for details of the options you can use.

Examples

 change_column(:suppliers, :name, :string, :limit => 80)
 change_column(:accounts, :description, :text)

Sets a new default value for a column. If you want to set the default value to NULL, you are out of luck. You need to DatabaseStatements#execute the appropriate SQL statement yourself.

Examples

 change_column_default(:suppliers, :qualification, 'new')
 change_column_default(:accounts, :authorized, 1)

A block for changing columns in table.

Example

 # change_table() yields a Table instance
 change_table(:suppliers) do |t|
   t.column :name, :string, :limit => 60
   # Other column alterations here
 end

Examples

Add a column

 change_table(:suppliers) do |t|
   t.column :name, :string, :limit => 60
 end

Add 2 integer columns

 change_table(:suppliers) do |t|
   t.integer :width, :height, :null => false, :default => 0
 end

Add created_at/updated_at columns

 change_table(:suppliers) do |t|
   t.timestamps
 end

Add a foreign key column

 change_table(:suppliers) do |t|
   t.references :company
 end

Creates a company_id(integer) column

Add a polymorphic foreign key column

 change_table(:suppliers) do |t|
   t.belongs_to :company, :polymorphic => true
 end

Creates company_type(varchar) and company_id(integer) columns

Remove a column

 change_table(:suppliers) do |t|
   t.remove :company
 end

Remove several columns

 change_table(:suppliers) do |t|
   t.remove :company_id
   t.remove :width, :height
 end

Remove an index

 change_table(:suppliers) do |t|
   t.remove_index :company_id
 end

See also Table for details on all of the various column transformation

Returns an array of Column objects for the table specified by table_name. See the concrete implementation for details on the expected parameter values.

Creates a new table with the name table_name. table_name may either be a String or a Symbol.

There are two ways to work with create_table. You can use the block form or the regular form, like this:

Block form

 # create_table() passes a TableDefinition object to the block.
 # This form will not only create the table, but also columns for the
 # table.
 create_table(:suppliers) do |t|
   t.column :name, :string, :limit => 60
   # Other fields here
 end

Regular form

 # Creates a table called 'suppliers' with no columns.
 create_table(:suppliers)
 # Add a column to 'suppliers'.
 add_column(:suppliers, :name, :string, {:limit => 60})

The options hash can include the following keys:

:id

Whether to automatically add a primary key column. Defaults to true. Join tables for has_and_belongs_to_many should set :id => false.

:primary_key

The name of the primary key, if one is to be added automatically. Defaults to id.

:options

Any extra options you want appended to the table definition.

:temporary

Make a temporary table.

:force

Set to true to drop the table before creating it. Defaults to false.

Examples

Add a backend specific option to the generated SQL (MySQL)

 create_table(:suppliers, :options => 'ENGINE=InnoDB DEFAULT CHARSET=utf8')

generates:

 CREATE TABLE suppliers (
   id int(11) DEFAULT NULL auto_increment PRIMARY KEY
 ) ENGINE=InnoDB DEFAULT CHARSET=utf8

Rename the primary key column

 create_table(:objects, :primary_key => 'guid') do |t|
   t.column :name, :string, :limit => 80
 end

generates:

 CREATE TABLE objects (
   guid int(11) DEFAULT NULL auto_increment PRIMARY KEY,
   name varchar(80)
 )

Do not add a primary key column

 create_table(:categories_suppliers, :id => false) do |t|
   t.column :category_id, :integer
   t.column :supplier_id, :integer
 end

generates:

 CREATE TABLE categories_suppliers (
   category_id int,
   supplier_id int
 )

See also TableDefinition#column for details on how to create columns.

SELECT DISTINCT clause for a given set of columns and a given ORDER BY clause. Both PostgreSQL and Oracle overrides this for custom DISTINCT syntax.

  distinct("posts.id", "posts.created_at desc")

Drops a table from the database.

Should not be called normally, but this operation is non-destructive. The migrations module handles this automatically.

Returns a Hash of mappings from the abstract data types to the native database types. See TableDefinition#column for details on the recognized abstract data types.

Removes the column(s) from the table definition.

Examples

 remove_column(:suppliers, :qualification)
 remove_columns(:suppliers, :qualification, :experience)

Alias for remove_column

Remove the given index from the table.

Remove the suppliers_name_index in the suppliers table.

  remove_index :suppliers, :name

Remove the index named accounts_branch_id_index in the accounts table.

  remove_index :accounts, :column => :branch_id

Remove the index named accounts_branch_id_party_id_index in the accounts table.

  remove_index :accounts, :column => [:branch_id, :party_id]

Remove the index named by_branch_party in the accounts table.

  remove_index :accounts, :name => :by_branch_party

Removes the timestamp columns (created_at and updated_at) from the table definition.

Examples

 remove_timestamps(:suppliers)

Renames a column.

Example

 rename_column(:suppliers, :description, :name)

Renames a table.

Example

 rename_table('octopuses', 'octopi')

Returns a string of CREATE TABLE SQL statement(s) for recreating the entire structure of the database.

Truncates a table alias according to the limits of the current adapter.

This is the maximum length a table alias can be

def tables(name = nil) end